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THE BOYS’ OWN BOOK 

OF SCIENCE 


BY 

FLOYD L/DARROW 

HEAD OF SCIENCE DEPARTMENT, POLYTECHNIC PREPARATORY COUNTRY 

DAY SCHOOL 

Author of “The Boys’ Own Book of Great Inventions,” “Masters of 

Science and Invention,” etc. 


V 1 

* ^ 

• > 

) ) > 

> - > 


j12rto gorft 

THE MACMILLAN COMPANY 

1923 


All rights reserved 


PRINTED IN THE UNITED STATES OF AMERICA 


Q,lb 3 

.J3a 


Copyright. 1923, 

By THE MACMILLAN COMPANY. 


Set up and printed. Published September, 1923. 



• * 

t ^ * 


Press of 

J. J. Little & Ives Company- 
New Y ork, U. S. A. 


SEP 26'23 

'feO >■ / 

©CU759U5 



PREFACE 


THE BOYS’ OWN BOOK OF SCIENCE has 
been written for that host of boys everywhere who 
wish to experiment at home. It is not a book about 
science. It is a practical guide to real worth-while 
experimental work. Under its direction the amateur 
will come to feel that he is not only acquiring knowl¬ 
edge, but that he is becoming a real scientist. The 
book has been written out of an experience of twenty 
years in teaching and in directing the home activities 
of boys in this sort of work. As an inspiration to their 
efforts, there have been included sketches of a number 
of world-famous scientists who started as home 
laboratory workers. 

It is not intended that every boy will do all of the 
experiments in this book. There is an abundance of 
material from which to select. Each boy may choose 
for himself that which most appeals to him. It will 
afford a browsing ground for a long period of time. 
Gradually real equipment may be accumulated and a 
genuine laboratory established. The laboratory is 
bound to grow with increased skill and a growing 
knowledge of fundamental processes. This book is 
not intended merely to entertain, although there will 
be entertainment in abundance. Its purpose is to direct 


vi Preface 

the latent energies of boys who wish to explore for 
themselves the fields of scientific discovery. Properties 
of matter, the nature of chemical and physical forces, 
and methods of preparing elements and compounds, 
as well as processes of analysis, have an irresistible 
appeal for all boys. This book has been written to 
satisfy that very legitimate interest. 

As a source book of information and experimental 
hints for teachers, this book may well be useful. 
Although not written for them, it contains much that 
will be of value, particularly to the beginning teachers 
of science. 

Floyd L. Darrow. 

Brooklyn, N. Y. 


CONTENTS 


CHAPTER PAGE 

1 The Home Laboratory. i 

2 Laboratory Manipulation. 8 

3 The Alchemist.14 

4 Chemical Magic.17 

5 Priestley and Scheele. 35 

6 Oxygen and Hydrogen.38 

7 Sir Henry Cavendish . 57 

8 The Atmosphere. 59 

9 Antoine Laurent Lavoisier. 7 1 

10 Acids, Bases, and Salts. 73 

11 The Examination of Water.89 

12 Sir Humphry Davy .n6 

13 Soap. n 9 

14 The Examination of Textile Fibers.127 

15 Michael Faraday. *34 

16 Stains and Bleaches .u6 

17 Jons Jakob Berzelius.h6 

18 Electric Furnaces.h8 

19 Some Metals and Their Alloys.164 

20 Justus von Liebig. *77 

21 More about the Chemistry of Combustion . . . 179 

vii 











Contents 


• • • 

viu 

CHAPTER PAGE 

22 Joseph Henry.200 

23 Fireworks.202 

24 Sir Henry Bessemer.214 

25 The Chemistry of the Electric Current . . . 216 

26 Sir William Perkin.235 

27 The Chemistry of Light.237 

28 Thomas A. Edison.247 

29 Special Tests.252 

30 George Westinghouse.271 

31 More Real Analysis.273 

32 Crystals.289 

33 Guglielmo Marconi.300 

34 Some Experiments in Physics.302 


35 The “Hall of Fame”. 323 














ILLUSTRATIONS 


Sir Humphry Davy—a home laboratory worker who be¬ 
came famous. Frontispiece 

PAGE 

Bending glass tubing with the “fish-tail” flame .... 9 

Igniting the wick of an alcohol lamp with a “glass rod” . . 19 

Generating sulfur dioxide, preparatory to changing “wine” 


into “water”.25 

Filling a flask with ammonia for a fountain in a vacuum . 31 

Burning steel wool in pure oxygen.43 

Generating carbon dioxide and collecting it over water . . 65 
Determining the strength of an acid by titration .... 79 

Distillation of water.91 

Testing for organic matter in water.107 

Making soap.121 

Determining the percentage of wool in a fabric . . . . 131 

Bleaching cotton fabric with chloride of lime.141 

Lampboard rheostat connected in series with an arc furnace 155 


Melting an alloy in hot water heated over an alcohol burner 169 
Burning air in an atmosphere of illuminating gas . . . . 183 

Extinguishing candles by pouring carbon dioxide upon them 195 
Throwing the switch for the ignition of flash powder . . 205 

Waiting for a flame to strike down and ignite the explosive 


mixture.209 

Electroplating.225 

Heating the copper spiral preparatory to making the test for 
wood alcohol.255 

Preparing chlorine water.275 

Making a blow pipe test for a metal.285 

Lifting 45 pounds with a homemade electromagnet . . . 311 


IX 














THE BOYS’ OWN BOOK 
OF SCIENCE 



THE BOYS’ OWN BOOK 
OF SCIENCE 


Chapter i 

THE HOME LABORATORY 

T HE location of the home laboratory is one of 
the most difficult problems that confronts the 
amateur experimenter. Most homes are not planned 
with any provision for his convenience and comfort. 
And yet, if at all possible, he should have a room— 
a small one will do—undisturbed by the rest of the 
family, where he may have perfect freedom to do real 
laboratory work. An upper room is preferable, and 
it should be as light and airy as possible. Of course 
a kitchen may be used as a laboratory, but apparatus 
and chemicals cannot be left standing around in it. 
And it is always a nuisance to have to get everything 
out and put it all away every time you wish tQ experi¬ 
ment. If possible, by all means have a permanent place 
to work. 

Now as to the equipment of your laboratory, that 
is a most important matter too. Across one side of 
your room build a bench about 30 inches high and 2 


2 


The Boys’ Own Book of Science 

feet wide. The top should be of hard wood and planed 
smooth. Paint it black and if possible cover it with 
slabs of plate glass. The glass will not be affected by 
any chemicals that you may use, and it can be easily 
kept clean. At one end of the bench you ought to have 
a sink with running water and waste pipe. Of course 
that is ideal. Many of you cannot have such luxurious 
quarters, and in that case you must bring water into 
your laboratory and carry it out each time that you 
experiment. At the bench should be a hose connection 
for illuminating gas. If your room is lighted with gas, 
this can be easily arranged. If you use electricity 
but have gas in the house, a plumber could probably 
run a pipe to your room without much trouble. Of 
course if gas is out of the question, you will have to 
substitute an alcohol lamp. And there are a number 
of good alcohol lamps on the market now which 
compare favorably in heat-giving power with a 
Bunsen burner. At the back and running the whole 
length of your bench build some shelves to hold your 
apparatus and chemicals. These do not need to be 
very deep. Six inches will be sufficient. As your 
laboratory grows and you accumulate larger pieces of 
apparatus, a cupboard may be built in another part of 
the room. 

The selection of apparatus and chemicals will require 
better judgment than any other feature of your equip¬ 
ment. It is usually not best to buy a regular chemical 
outfit. At the start such an outfit will be more or less 
of a mystery to you. Frequently the apparatus is not 


The Home Laboratory 3 

of the highest quality and the quantities of chemicals 
are small. The most economical and satisfactory 
method is to select a certain number of experiments 
from the following chapters which you wish to do. 
Note fhe pieces of apparatus and materials which you 
will need and then order them of a reliable firm. You 
will find that many of these materials are very com¬ 
mon. Some of them you will find in your own house¬ 
hold. Others may be had from the druggist or the 
grocer. A large granite basin and wide-mouth bottles 
will serve for the collection of gases. Apparatus must 
be ordered from some chemical company. . 

But if you build your laboratory in this way, it will 
grow with your knowledge. You will know the pur¬ 
pose of every piece of apparatus and every chemical. 
When you are through, your laboratory will represent 
a personal creation. Your experience will have genuine 
educational value and not be a mere entertaining 
pastime of which you will soon grow weary. 

To aid you in the selection of apparatus I have 
arranged two cuts that show many of the principal 
pieces which sooner or later you will need. If at any 
time you do not know what is meant by a certain piece 
of apparatus, refer at once to these illustrations and 
their names in the footnotes. 

Of course you will need a Bunsen burner or an 
alcohol lamp, a ring-stand, a wire gauze with asbestos 
center, some test tubes, a few rubber stoppers of 
various sizes, several lengths of glass tubing about 
five-sixteenths of an inch outside diameter, four feet 



Figure i. 

LABORATORY APPARATUS. 

i. nest of beakers; 2. Bunsen burner; 3. hornpan balance; 4, retort; 5, set of 
weights; 6, test-tube holder; 7, burette; 8, pipette; 9, thistle tube; 10, tripod; 
11, Erlenmeyer flask; 12, gas generator; 13, water bath; 14, blowpipe: 1 z 
wash bottle. 
























































Figure 2. 

LABORATORY APPARATUS. 

16, test-tube rack; 17, pneumatic trough; 18, steel forceps; 19,. ring-stand; 
20, crucible and lid; 21, funnel; 22, iron deflagrating spoon; 23, pipestem 
triangle; 24, test-tube brush; 25, mortar and pestle; 26, clamp; 27, alcohol 
lamp; 28, glass cylinder; 29, porcelain evaporating dish; 30 pinch clamp, 31, 
flask. 
































6 The Boys Own Book of Science 

of rubber tubing to fit, a flask of 500 cubic centimeters’ 
capacity, an Erlenmeyer flask half as large, a small 
evaporating dish, a mortar and pestle, a pair of steel 
forceps, and a porcelain crucible and lid. Other needs 
will present themselves as you proceed with the work. 

All volumes of liquids will be measured in cubic 
centimeters and weights of chemicals will be in grams, 
since the metric system is everywhere used in scientific 
work. You will need a graduate of about 25 
cubic centimeters 1 capacity and a hornpan balance and 
weights. These need not be expensive. The weights 
should go from 1 gram to 50 with additional decimal 
weights running from 0.01 to 0.5 of a gram. In all 
future directions I shall use the abbreviations c.c. for 
cubic centimeters and g. for grams. 

Another quite important item of your equipment 
will be the matter of electricity. For some of the 
work, I will direct you later how to make simple cells 
that will be perfectly satisfactory. But if you are to 
do any of the work that I describe with electric fur¬ 
naces, another source of supply will be essential. If 
you have electricity in your house, the problem may be 
easily solved. Wires may be run to a couple of bind¬ 
ing posts on your bench and you will have available at 
all times 110 volts. For electric heat, either direct or 
alternating current will serve your purpose. If the 
voltage is to be cut down by a resistance and the cur¬ 
rent used for most other work in place of cells, direct 
will be required. You must remember always that in 
using a 110-volt source of current a considerable 


7 


The Home Laboratory 

resistance must be placed in series with your apparatus, 
if you are not to blow the fuses or possibly ruin your 
apparatus. But I will give you directions about resist¬ 
ances when the experiments are described. If it is not 
convenient to run wires to your bench, a connection 
may be made to a lamp socket. Between the binding 
posts on your bench or the wires from the lamp socket 
and your apparatus always place a switch. Then if 
trouble arises you may easily break the circuit. 

In starting this work make up your mind that you 
are going to become a real home laboratory worker. 
Do not let your chief purpose be amusement only, 
although genuine enjoyment you will get in abundance. 
Have in your laboratory a shelf of the latest texts of 
elementary chemistry and study the subject as you 
proceed. Add to your library whenever possible. You 
will be surprised and delighted to see how rapidly your 
working knowledge of chemistry will expand. And it 
may quite possibly be that this amateur work will prove 
to be a stepping-stone to your future career. The 
director of one of the largest technical schools in New 
York said in a letter to me the other day that the 
demand for men with laboratory training far exceeds 
the supply. You may qualify to meet this demand, 
and your initial training may be had in your own 
laboratory. 


Chapter 2 


LABORATORY MANIPULATION 

T here is much to learn regarding the care of 
apparatus and its use in the laboratory. Grad¬ 
ually you will acquire the technique of laboratory 
practice. At the start a few simple directions will be 
of value. 

The Burner.—Examine your Bunsen burner and 
note how it is made. Observe that there are holes 
at the bottom of the tube for the admission of air, and 
an air adjustment. In lighting the burner turn the 
gas on full and hold the match two or three inches 
above the top of the tube. If these precautions are 
not observed, the flame will unusually “strike back” 
and burn at the base. Whenever this happens, turn off 
the gas immediately and relight it. If you wish to 
obtain a small flame, with the air adjustment cut off 
some of the air and at the same time turn down 
the gas. Note that when the air-holes are completely 
closed, the flame is luminous. Such a flame deposits 
soot and is seldom used. Always use the clear blue 
flame. 

Glass Cutting.—Very often you will have occasion 
to cut glass tubing. To do so make a slight groove 

with a triangular file at the point where you wish to cut 

8 







Bending glass 


tubing with the 


“fish-tail” 


flame. 


9 












Laboratory Manipulation 11 

it. Then grasping the tube with both hands, the 
thumbs meeting opposite to the grove, bend the ends 
of the tube toward you. T his should give an even 
break. 

Before using glass tubing, fire polish the ends. To 
do this hold each end of the tube in the flame for a few 
moments rotating it, as you do so. The glass will 
soften and leave a smooth edge in place of the sharp 
ragged one. 

Glass Bending.—Another very important operation 
is the bending of glass tubing. This will be necessary 
in making angle-tubes for rubber stoppers and de¬ 
livery tubes for collecting gases. 

In bending glass place a “fish-tail” top on your 
burner so as to obtain a broad flat flame. Then hold¬ 
ing the tubing lengthwise of the flame rotate it with 
your fingers in order to heat it evenly on all sides. In a 
few moments the glass will soften and, when the flame 
is colored an intense yellow, you may remove the tub¬ 
ing and bend it quickly to the desired shape. The bend 
should always be broad and round, instead of sharp 
and angular. Then it will not easily break. 

Stoppers.—For most purposes rubber stoppers are 
best. They come in sizes numbered from o-o to io 
and even higher. For your work the first six sizes will 
probably be sufficient and you should have two or three 
of each. It is always best to get two-hole stoppers, 
except in the first three sizes. Then if you need a one- 
hole stopper you may easily close one hole with a glass 
plug. To make a plug hold with the tongs an inch 


12 


The Boys’ Own Book of Science 

length of glass tubing vertically in the flame until the 
opening is closed. 

In passing a piece of glass tubing through a stopper 
do not force it. That will usually break the tubing. 
Moisten both tubing and stopper and the stopper will 
slip on easily. 

Corks of various sizes may probably be obtained 
from your druggist. For making holes in them you 
will need a set of cork-borers which you will readily see 
how to use. To bore a hole in a rubber stopper 
wet the boring tube in dilute sodium hydroxide solu¬ 
tion. 

Heating Glassware and Porcelain.—A test tube 
may be held directly in the flame, but beakers and 
flasks must be protected by a wire gauze. It is best 
to have one or two 4-inch squares of gauze with an 
asbestos center. In heating any glass apparatus con¬ 
taining a liquid, never allow the flame to extend above 
the level of the liquid. Vessels like bottles and bat¬ 
tery jars having thick walls can never be heated. Por- 
celainware may be heated to a high temperature, but 
the heat should be applied gradually. Crucibles may 
be put directly in the flame but evaporating dishes 
should be protected by a wire gauze. 

General Hints.—Before you actually begin to per¬ 
form an experiment have everything in readiness. 

Clamp all glass apparatus loosely, especially if it is 
to be heated. 

Do not force stoppers into the necks of thin glass 
flasks or test tubes. 


Laboratory Manipulation 13 

Always be sure that the lower end of a thistle tube 
dips beneath the liquid in the flask. 

In removing a stopper from a reagent bottle do not 
lay it down. With the palm of the hand turned up¬ 
ward, remove the stopper by pressing it between the 
lower joints of the first and second fingers. Then 
grasp the bottle between the thumb and lower fingers. 
After pouring out the reagent remove the drop clinging 
to the lip of the bottle by touching it to the receiving 
vessel and replace the stopper. 

Folding Filter Paper.—You will frequently have 
occasion to filter liquids. Fold the circular piece of 
filter paper in half. Then fold it in half again. When 
opened up this will exactly fit the angle of your funnel. 
Press the filter against the sides of the funnel, and 
moisten it with a few drops of water to hold it in 
place. Filtering is a slow process, but a properly 
fitted filter will greatly hasten the operation. 

Quantities of Material.—Do not adopt the plan that 
“if a little is good more is better.” In making tests, 
very small quantitits give much more decisive results 
than large ones. Wherever the amounts are not speci¬ 
fied, use small ones. 


Chapter 3 
THE ALCHEMIST 


T HE original home-laboratory experimenter was 
the alchemist. Possibly you have never heard 
of him. He was a curious type of scientist, but there 
were many of them scattered throughout Europe all 
during the Middle Ages and even down to quite mod¬ 
ern times. They worked in dark caves and hidden 
places, keeping their discoveries secret from other 
men. 

There was a mythical story abroad during those 
early centuries about a wonderful substance known as 
the “Philosopher's Stone.” Whoever should be able 
to find or make this magic stone would be in possession 
of everything that men might desire. At its touch 
the baser metals would at once turn into gold and 
its mere presence would give to the fortunate possessor 
perfect health and perpetual youth. In the ignorance 
and superstition of those days no tale seemed too fan¬ 
tastic for belief. Indeed, there seemed much evi¬ 
dence in support of this idea of changing one metal 
into another. Iron rusted, and, as they thought, a 
new substance formed. If a rod of iron were thrust 
into a solution of blue vitriol, the iron disappeared and 
metallic copper took its place. What more natural 

14 


The Alchemist 


15 

than to suppose that iron had been transformed into 
copper ? Were not gold and silver actually found in 
lead ore, and did not this indicate that these precious 
metals were transmuted lead? And, too, it was be¬ 
lieved that worked-out mines after long periods of 
time exhibited new “crops” of gold and silver. Could 
they not learn the secret of this change and be able to 
control it? For centuries men pursued this will-o’-the- 
wisp. Strange, it seems now, doesn’t it? 

Many was the impostor who rose to prey upon the 
credulity of king and prince and obtain ill-gotten gain 
under the false pretense of having found this magic 
substance. An old alchemist was one day giving a 
dinner to some friends when, with much unconcern, he 
related an incident from his personal experience that 
had occurred eight hundred years before. Noting the 
looks of amazement upon the faces of his guests, he 
turned to his servant and said, “John, is not that true?” 
And the faithful servant replied, “You forget, master, 
that I have been in your service but five hundred 
years.” 

But although the philosopher’s stone was never 
found, the search for it resulted in much gain for 
chemistry. New substances were found or made. 
These workers became expert in laboratory methods. 
Many of the new drugs were useful as medicines, and 
gradually there grew out of alchemy the art of the 
apothecary. In fact this search for the healing prop¬ 
erties of new compounds in time became the chief pur¬ 
pose of chemistry. But in their eagerness to discover 


16 The Boys’ Own Book of Science 

the curative effects of some new-found drug these 
crude practitioners hastened to administer it to some 
patient instead of first trying it out on a cat or dog. 
Indeed, it was in this way that the fatal properties of 
our violent poisons were made known. 

But the real chemist in time took the place of this 
misguided seeker after the impossible, and soon you in 
your home laboratory will be in possession of more real 
chemical knowledge than all the alchemists ever knew. 


Chapter 4 
CHEMICAL MAGIC 

I AM sure the users of this book of home laboratory 
experiments are not going to be much different 
from the large number of other boys whom I have been 
directing in this kind of work for a number of years. 
It is the mysterious and wonderful things in chemistry 
and physics that always appeal to beginners. So I am 
going to start you off with some experiments on chemi¬ 
cal magic. Gradually we shall come to more serious 
things and work of real chemical importance. The 
experiments in this first chapter will give you an 
abundance of material, not only for your own amuse¬ 
ment but for parlor entertainments. 

The National Colors.—Let us begin by being patri¬ 
otic. Place on the table before you a glass pitcher and 
three tumblers. Pill the pitcher with water into which 
you have stirred a few c.c. of a solution of ferric chlo¬ 
ride. To all appearances the water will be nearly 
colorless. In the first tumbler place two or three drops 
of a solution of ammonium sulfocyanate. Leave the 
second tumbler with nothing in it. In the third, place 
two or three drops of potassium ferrocyanide solution. 
You should have these preliminaries arranged in ad¬ 
vance. Then announce to your audience that you will 



18 The Boys’ Own Book of Science 

pour the national colors from a pitcher of pure water. 
Upon filling the tumblers, the first will be a deep red, 
the second colorless, and the third a bright blue. Like 
all trick experiments this will be perfectly mystifying 
to the uninitiated but quite clear to you. The iron 
compound used, when present even in small quantities, 
gives with these indicators the characteristic colors 
observed. 

“Freezing” Water by Magic.—Into a small flask 
or breaker put 50 g. of ordinary photographer’s hypo 
and 10 c. c. of water. (A small hornpan balance and 
graduate will enable you to get these quantities with¬ 
out difficulty). Heat this mixture over your alcohol 
or Bunsen burner until the hypo just dissolves. Then 
let it cool carefully without disturbance. A clear liquid 
solution will result. Have at hand a tiny crystal of 
hypo about as big as a pinhead. Holding the flask 
before your audience, state that in the twinkling of an 
eye you will freeze this water to solid ice. Dropping 
the crystal into the solution, give the flask a quick shake 
and immediately its contents will change to a mass of 
solid crystals. At the same time the flask will become 
decidedly warm giving experimental evidence of the 
fact that when water freezes or a solid crystallizes 
heat is given off. You have prepared in this experi¬ 
ment what we call a supersaturated solution, and when 
the crystal is added the water recombines chemically 
with the hypo to form the original crystals again. But 
to your observers it appears like the actual freezing of 
water. 



Igniting the wick of an alcohol lamp with a “glass rod.” 


19 





21 


Chemical Magic 

Igniting Gasoline with a Glass Rod.—Place on your 
demonstration table a small pane of window glass, a 
beaker, and a glass rod. In the bottom of the beaker 
put a half teaspoonful of potassium permanganate 
crystals and moisten them with a few drops of water. 
Pour on the window pane two tablespoonfuls of gaso¬ 
line. Add two or three cubic centimeters of the strong¬ 
est sulfuric acid to the contents of the beaker. Imme¬ 
diately a vigorous chemical action will be set up. Then 
dip the glass rod into the sputtering mixture and touch 
it to the gasoline. With a flash the gasoline will take 
fire and blaze up. 

If the rod is again dipped into the mixture and 
touched to the wick of an alcohol lamp, the wick will 
light. The chemicals in your beaker have produced 
ozone, a very concentrated form of oxygen, and this 
has oxidized the gasoline and alcohol rapidly enough 
to bring them to their kindling temperatures. 

Some Mystifying Color Experiments.—Arrange 
three rows of tumblers on your table and a pitcher of 
water containing one or two tablespoonfuls of strong 
household ammonia. In the bottom of each tumbler 
in the first row place two drops of phenolphthalein in¬ 
dicator. This indicator is prepared by dissolving a 
tiny pinch of phenolphthalein powder in a little de¬ 
natured alcohol. To each tumbler in the second row 
add a few drops of strong sulfuric acid. Two or three 
will probably be enough. To the tumblers in the third 
row add a few drops of a strong solution of sodium 
hydroxide, or lye. 


22 


The Boys* Own Book of Science 

Begin to fill the first row of tumblers and behold 
from your pitcher of “water” will apparently come 
forth “wine.” Then, stating that you wish to get rid 
of this dangerous evidence, pour the contents of the 
first row of tumblers into the second. Immediately 
the wine changes back to water. And, upon pouring 
the water into the third row of tumblers, the wine 
reappears. 

Just exactly what has happened will become clear 
when we have had some later work on acids and bases. 

Freezing a Tumbler to a Block of Wood.—Upon 
a smooth block of wood place a few drops of water and 
set in it a thin-glass tumbler. Fill the tumbler an 
eighth full of water and stir into it ammonium nitrate 
powder in considerable quantity. Presently moisture 
will condense upon the outside of the tumbler, then 
frost will appear, and finally the tumbler will freeze to 
the block so that you can pick it up and the block 
will not fall. The solution of ammonium nitrate pro¬ 
duces great “cold.” 

This same stunt may be done by blowing through 
a glass tube into ether or carbon disulfide placed in 
the tumbler. The evaporation of the liquid also pro¬ 
duces cold. 

Obtaining Water from Solid Crystals.—Place in a 
dry test tube a few crystals of native gypsum, that is, 
gypsum just as it comes from the mine. Heat the test 
tube holding it so that it will slant gently downward. 
Almost immediately steam will appear and moisture 
will condense on the cold walls of the tube. Presently 


Chemical Magic 23 

drops of water will drip from the mouth of the tube. 
And there is a most remarkable fact about this water. 
It has been locked up in these crystals for millions of 
years. Any gypsum that is now quarried was formed 
in the earth’s crust ages ago, and the imprisoned water 
fell as rain in a far distant past. And yet the water 
is the same in composition as water produced now. It 



Figure 3. 

Apparatus for preparing sulfur dioxide and converting “wine” into “water.” 
Potassium permanganate is in cylinder at left. 


is perfectly pure and, could you get enough of it, fit 
to drink. Upon examining the residue in the tube you 
will find that the gypsum has lost its crystal form and 
may be crumpled to a powder. 

The same experiment may be repeated with crystals 
of blue vitriol and photographer’s hypo. But in these 
cases the salts have been artificially prepared and the 
water is not of ancient origin. 

Changing “Wine” into Water.—There is another 
color experiment more baffling than any of the pre- 






















24 The Boys’ Own Book of Science 

ceding. In a clear-glass pitcher prepare a purple solu¬ 
tion, resembling wine, by pouring water onto a few 
crystals of potassium permanganate. Then set up a 
sulfur dioxide generator as shown in figure 3. The 
generator may be a wide-mouth bottle to which you 
have fitted a thistle tube and delivery tube. In the 
generator place sodium sulfite and having arranged for 
the collection of the gas, as indicated, pour through the 
thistle tube a little hydrochloric acid. Immediately a 
vigorous action will begin and heavy sulfur dioxide gas 
will pass through the delivery tube and fill the receiving 
cylinder or bottle. You can tell when the cylinder is 
full by the abundance of sharp choking fumes that 
come from about its mouth. In filling a cylinder with 
gas in this way, always pass the bent delivery tube 
through a perforated cardboard cover. 

Now remove the delivery tube and cover the cylinder 
with a glass plate. Have the gas generated in advance 
of your audience. Since sulfur dioxide is a colorless 
gas, the cylinder will appear to be perfectly empty. 
Then announce that you are to accomplish the magic 
transformation of wine into water. Upon pouring the 
purple potassium permanganate solution into the sulfur 
dioxide cylinder, the color will disappear just as fast as 
you can pour it, and apparently water will have formed. 
The sulfur dioxide really reduces the permanganate to 
a colorless compound. 

The Magic Wand.—You will find it easy to pro¬ 
duce a color change which will appear only after an 



Generating sulfur dioxide, preparatory to changing “wine” into “water.” 


25 













Chemical Magic 27 

interval of time and at the precise moment that you 
wave your magic wand. 

Prepare a solution of sodium iodate by dissolving 
one gram of the substance in a pint of water. Stir into 
this a few c. c. of thin starch paste made by pouring 
boiling water on to a pinch of starch and allowing 
it to cool. Fill a large tumbler half full of the mix¬ 
ture. 

Then using the same apparatus as that of the pre¬ 
vious experiment, prepare a solution of sulfur dioxide 
by bubbling the gas for a few moments through a half 
pint of water. 

Now pour the sulfur dioxide solution into that of 
the iodate and mix thoroughly. Nothing seems to 
happen at first, but in from one to five minutes, de¬ 
pending upon the strengths of the solutions, a deep 
purple color will suddenly spread throughout every 
portion of the mixture. By timing this interval you 
will be able to determine just exactly how many min¬ 
utes and seconds will elapse between mixing the solu¬ 
tions and the appearance of the color. Then at the 
psychological moment wave your wand and behold the 
color. 

Changing “Air” to Brown Fumes.—Using the sul¬ 
fur dioxide generator, arrange your apparatus as 
shown in Figure 4. In the generator place a few 
copper rivets. For the pneumatic trough, over which 
to collect the gas, a granite basin containing an inch- 
depth of water may be substituted. Fill a wide- 
mouth bottle with water and covering it with a glass 


28 The Boys’ Own Book of Science 

plate invert it in the basin, leaving the bottle filled 
with water. 

Now nearly cover the copper rivets with water and 
pour through the thistle tube strong nitric acid. Soon 
the generator will begin to bubble and fill with brown 
fumes. Then placing the delivery tube beneath the 



Preparation of nitric oxide for changing “air” to brown fumes. 

slightly upturned mouth of the bottle, fill the bottle 
with gas, which will rise through the water and 
displace it. If you like, several bottles may be filled 
with the gas. To remove them place glass plates 
beneath their mouths and invert them upon the 
table. 

The gas in the bottles is colorless, but, upon remov¬ 
ing the glass plates so that the air may act upon it, 






























Chemical Magic 29 

dense brown fumes appear. It seems like changing the 
color of air. 

If a little water is shaken in the bottle, the fumes 
dissolve giving a colorless solution, which turns red 
upon adding a solution of blue litmus. 

Something from Nothing.—Dissolve three or four 
tablespoonfuls of granulated sugar in as little water as 
possible. Place the solution in a tall tumbler or jar. 
Then pour into it an equal quantity of the strongest 
sulfuric acid. Immediately the mixture turns black, 
begins to steam, and presently it boils up and fills the 
tumbler to overflowing with a thick black mass of 
frothy carbon, while the odor of burnt sugar fills the 
air. It will be amazing to see the large mass of solid 
material that will come from so small a quantity of 
sugar. 

The sugar consists of carbon together with hydrogen 
and oxygen in proportion to form water. Sulfuric 
acid has a very great affinity for water and removes the 
hydrogen and oxygen leaving the black carbon. 

Queer Forms of Sulfur.—Ordinary sulfur, or brim¬ 
stone, is easily obtained. Fill a test tube two-thirds 
full of broken pieces and heat them very slowly in the 
flame, taking the tube out frequently to prevent a too 
rapid heating. Gradually the sulfur will melt into a 
clear straw colored liquid. Then upon further heating 
this liquid will change to a thick cherry-red substance 
which will not flow from the test tube even when in¬ 
verted. It looks like jelly and good enough to eat. 
When heated again, the color becomes nearly black, 



30 The Boys f Own Book of Science 

and the sulfur changes to a thin boiling liquid. Have 
at hand a jar of water and quickly pour the boiling 
sulfur in a thin stream into the water. Probably the 
sulfur vapor will take fire, giving an example of spon¬ 
taneous combustion, but don’t be alarmed at that. Re¬ 
move the sulfur from the water and you will find a 
rubbery mass, which will stretch like elastic. Upon 
standing for twenty-four hours it will change back to 
the original brittle form. 

Sympathetic Ink.—Dissolve a pinch of cobalt chlo¬ 
ride in a little water and write your name with it upon 
white paper. When dry, nothing will be visible. But, 
if the paper is held high above the flame of an alcohol 
or Bunsen burner, the letters will appear in blue lines. 
As it cools, the letters will gradually fade. 

You may prepare in advance some mysterious mes¬ 
sage and state to your audience that you have a spirit 
communication which will appear only under the influ¬ 
ence of fire. Show them that the magic paper has no 
writing upon it. Then go through certain incantations 
at the same time holding the paper above the flame. 
Presently the message will be revealed. 

Magic Writing Papers.—Prepare three mixtures, 
each of which will contain powdered ferric ammonium 
sulfate, and in addition in number one an equal quan¬ 
tity of powdered potassium ferrocyanide in number 
two tannic acid, and in number three ammonium 
sulfocyanate. 

Keeping all materials perfectly free from moisture, 
rub one piece of white writing paper over thoroughly 





Filling a flask 


with ammonia for a fountain in a vacuum. 


31 














33 


Chemical Magic 

with mixture number one, another with mixture num¬ 
ber two, and a third with mixture number three. Shake 

off any loose powder and then write with water upon 
each paper. The letters will appear blue in the first, 
black in the second, and red in the third. 

Changing one Metal into another.—Prepare a solu¬ 
tion of blue vitriol and fill a cylinder or tall narrow 
bottle with it. I hen thrust into the solution a strip of 
sheet zinc. Immediately the zinc will become dis¬ 
colored and gradually it will disappear. At the same 
time the blue color disappears from the solution and 
a deposit of red copper will accumulate in the cylinder. 
The zinc has gone into solution and displaced the cop¬ 
per. The alchemists regarded this as the actual 
transformation of one metal into another. 

Producing a Magic Fountain.—Arrange apparatus 
as shown in the illustration. Fill the flask over the 
Bunsen burner a third full of the strongest household 
ammonia. In the large glass jar beneath the inverted 
flask place water containing litmus solution and two or 
three drops of sulfuric acid. T his will color the water 
red. Have a one-hole rubber stopper carrying a 
glass tube extending up into the flask arranged as 
shown and dipping into the liquid in the jar below. 
Then heat the ammonia and drive the gas through 
the delivery tube into the inverted flask. Since the 
gas is light, it will rise and displace the air. When 
the flask is full, which may be told from the strong odor 
of ammonia about the mouth of the flask, inject into 
the flask a little water from a medicine dropper and 



34 The Boys Own Book of Science 

tightly insert the stopper and long jet-tube. The 
water will slowly rise until it reaches the top of the 
tube, when it will come with a rush filling the flask with 
a beautiful fountain and at the same time the color of 
the water will change from red to blue. Ammonia is 
so soluble in water that as soon as the fountain starts a 
vacuum is created and the water continues to rise until 
the flask is nearly or quite full. Since the ammonia 
water is a base it changes the red litmus to blue. 

These by no means exhaust the number of magic 
experiments that will appear in this book. Others 
will follow in the regular work of experimentation and 
special tests. 


Chapter 5 

PRIESTLEY AND SCHEELE 


P RIESTLEY and Scheele. When we hear these two 
names, we at once think of oxygen, for they were 
the discoverers of this important gas. And they were 
home-laboratory workers. Most of the early 
scientists were. High school and college laboratories 
did not then exist. And science in those days pre¬ 
sented a veritable paradise of undiscovered possibil¬ 
ities. Most of the elements and their compounds 
were unknown. Almost any persistent experimenter 
might blunder onto some new discovery. But Priestley 
and Scheele were not blunderers. They were two of 
the most skillful chemists of their time. Priestley 
was an Englishman and Scheele a native of Sweden. 

Priestley was forty before he began to experiment 
much. He was a clergyman who became interested in 
the study of gases. Many of the present pieces of gas 
apparatus were devised by him. One day he placed 
some red powder, now known as mercuric oxide, into 
a glass container and began to heat it. To obtain 
heat in those days was a difficult matter. Gas and the 
Bunsen burner were unknown, and the spirit lamps 
crude and inefficient. Priestley employed a large 
twenty-inch burning glass and focused the rays of the 

35 


36 The Boys Own Book of Science 

sun upon his apparatus. The composition of this 
powder was unknown to him. Presently he noted that 
the contents of the tube turned dark in color. Then a 
silvery deposit appeared on the cooler portion of the 
tube and a gas began to bubble up through the water 
of his pneumatic trough. Surely he was making a dis¬ 
covery. He collected some of the gas. Finally he ob¬ 
tained a large bell-jar of it. To his surprise and 
delight, he found that substances burned in it with 
wonderful brilliancy. A mouse placed in the gas be¬ 
came very lively, and he himself was greatly invigor¬ 
ated by breathing it. Here was a new element, and 
Priestley immediately published his discovery. This 
was in 1774. 

But at least two years earlier Scheele had also dis¬ 
covered this same gas but did not publish the fact until 
after Priestley had made his announcement. There¬ 
fore both may lay equal claim to this honor. Scheele 
was a poor apothecary’s apprentice who worked 
throughout his short life of forty-three years in what 
we should call now a crude home laboratory. But 
he made remarkable discoveries. He discovered the 
poisonous gas chlorine and its bleaching properties. 
He perfected new methods of analysis and became the 
first great master of qualitative analysis. He carried 
out brilliant researches in organic chemistry and may 
be regarded as the founder of this important branch of 
the subject. Before he died he had been honored by 
the leading scientific societies of Europe and every 
school hoy is now familiar with his name. 


37 


Priestley and Scheele 

It is interesting to know that Priestley passed the 
last ten years of his life in this country and lies buried 
on the banks of the Susquehanna. Some of his orig¬ 
inal apparatus is now in the museum of Dickinson 
College at Carlyle, Pennsylvania. 








Chapter 6 

OXYGEN AND HYDROGEN 

O XYGEN and hydrogen are two of the most im¬ 
portant and widely distributed elements with 
which you will have to deal. The food you eat, the 
water you drink, and your own bodies contain both of 
these elements in combined form. The air is one-fifth 
oxygen, and all living things are largely compounds of 
oxygen and hydrogen together with carbon. 

And right here we must distinguish between an ele¬ 
ment and a compound. An element is a substance that 
cannot be changed by any known means into anything 
different from itself. Of course radium does change 
into other elements, but we can do nothing to influence 
the process. There are something over Bo known 
elements, and each one has properties, or character¬ 
istics, which make it different from every other element. 
For instance hydrogen burns and oxygen supports com¬ 
bustion. Gold is yellow and silver is white. And no 
matter where an element is found its properties are 
always the same. But a compound is a chemical union 
of two or more elements in which the elements have 
lost their characteristic properties and can be separated 
only by chemical means. Water is a chemical com¬ 
pound of hydrogen and oxygen. You never would 

38 




Oxygen and Hydrogen 39 

suspect that water may be decomposed into two 
gaseous elements, one of which will burn and the other 
support combustion. The hydrogen and oxygen in 
uniting to form water have lost their own characteristic 
properties and have formed a totally new substance. 
To separate this new substance into its elements some 
kind of chemical means must he employed. We shall 
see what is meant by chemical means as we proceed. 



Apparatus for the preparation and collection of oxygen. 

Preparation of Oxygen.—Oxygen is the most abun¬ 
dant element known. Forty-seven per cent of the 
earth’s crust is oxygen and eight-ninths of the ocean. 
It exists in many compounds, and some of them give it 
up readily. We shall select for our purpose in pre¬ 
paring it potassium chlorate. 

Mix thoroughly two teaspoonfuls of powdered pot¬ 
assium chlorate with about one fourth that bulk of 
manganese dioxide. If you have a balance and weights, 
you may make a mixture of 8 grams of the chlorate and 














40 The Boys Own Book of Science 

6 grams of the dioxide. Place this mixture in a test 
tube fitted with a one-hole rubber stopper and delivery 
tube. For a pneumatic trough you may use a large 
basin (Fig. 5). Fill it nearly half full of water and 
invert in it a half dozen bottles full of water. To do 
this cover the bottle with a glass plate, quickly invert it, 
and when the mouth is beneath the water in the basin 
remove the plate. When all is ready, light your Bun¬ 
sen burner or alcohol lamp and begin gently to heat 
the test tube, moving the flame about so as not to heat 
the mixture all in one spot. It will be best to have an 
assistant in this experiment. Let him tip one of the 
bottles slightly with one hand and with the other 
slip the end of the delivery tube beneath its mouth. 
Presently the gas will begin to come very rapidly, and 
one bottle after another may be filled until they are all 
full. If the gas is then still coming, hold in it a glow¬ 
ing stick and note the brilliancy with which it burns. 
This is the test for oxygen. You will observe that the 
oxygen seems to be white, but this is due to the presence 
of vapor and it will disappear upon standing over 
water for a short time. 

Now why did we add the manganese dioxide? To 
determine this heat a little potassium chlorate by itself 
in a test tube, holding it with a test tube holder over 
the flame. The substance will melt and then boil. At 
that point thrust into the tube a glowing splint. It will 
burst into flame showing the presence of oxygen. Now 
allow the tube and contents to cool until oxygen just 
fails to be given off. I hen add a pinch of manganese 


41 


Oxygen and Hydrogen 

dioxide, and immediately oxygen in large volume will 
escape. Don’t you see, manganese dioxide lowers 
the temperature and increases the rapidity with which 
oxygen will be liberated? 

Oxygen from Sodium Peroxide.—Oxygen may also 
be very readily prepared by the action of water on 
sodium peroxide. Place some of this powder which 
comes in a sealed can and must be kept sealed, in your 
gas generator. (See figures of apparatus in chapter 
I.) Connect to it your delivery tube, the same as 
that used in the previous experiment and consisting of 
about two feet of red rubber tubing attached to a piece 
of glass tubing having its end slightly curled up. 
Through the thistle tube pour some water, being sure 
that the end of the tube nearly touches the bottom of 
the generator. Immediately the oxygen will begin to 
come off at a very rapid rate and may be collected over 
water in the usual way. 

There are other methods of preparing oxygen, but 
these two are the simplest. 

Burning in Oxygen.—You do not need to be told 
that all burning, or combustion, is due to the union of 
oxygen with other substances. To discover for our¬ 
selves the brilliancy of combustion in pure oxygen, we 
shall perform the following experiments. 

Burning Steel Wool.—Let us start off with a real 
spectacular display. T urn up the end of a stout wire 
hook-shape and fasten to it a bunch of steel wool. If 
you do not have steel wool, unravel some picture cord 
wire and make it. Slip a glass plate beneath the mouth 


42 The Boys' Own Book of Science 

of one of your bottles of oxygen and invert it upon the 
table, leaving it covered with the plate. Have at hand 
a small heap of powdered sulfur. Heat the wire in 
the Bunsen flame and touch it to the sulfur. Some of 
the sulfur will take fire and cling to the wire. Imme¬ 
diately remove the glass plate from the jar and thrust 
into it the ignited wool. The combustion will be of 
dazzling brilliancy accompanied by a shower of sparks. 
If this can be done in the dark, the vividness will be 
much increased. 

Combustion of Magnesium.—Wind 4 or 5 inches 
of magnesium ribbon about a length of stout iron wire, 
allowing the lower end of the ribbon to project a little. 
Ignite this end by touching it to the Bunsen burner 
flame and quickly thrust it into a bottle of oxygen. 
Again there will be a flash of blinding light. 

Combustion of Phosphorus.—Line the bowl of your 
deflagrating spoon with asbestos paper and place in it 
a little red phosphorus. Ignite the phosphorus in the 
flame and lower the spoon into a bottle of oxygen. 
The combustion is brilliant and a white cloud of phos¬ 
phorus pentoxide will fill the jar. 

Burning of Powdered Charcoal.—In the bottom of 
a dry pint milk bottle place a layer one-fourth inch 
deep of finely powdered willow charcoal which has been 
previously dried in an oven. Prepare a fresh mixture 
of potassium chlorate and manganese dioxide and gen¬ 
erate more oxygen, but this time thrust the delivery 
tube to the bottom of the bottle and direct the stream 
of gas so that it will produce a cloud of charcoal dust. 




Burning steel wool 


in pure oxygen. 


43 







Oxygen and Hydrogen 45 

Then remove the delivery tube and immediately apply 
a flame by means of a long wax taper. The combus¬ 
tion will be explosive, but there will be no danger from 
it. 

Burning of Powdered Iron or Zinc Dust.—Repeat 
the previous experiment, but substitute powdered iron 
or zinc dust for the charcoal. In order to protect your 
eyes from the blinding light, it will be necessary to 
wear colored glasses. 

Combustion of Sulfur.—Again line the bowl of your 
deflagrating spoon with asbestos and place in it a piece 
of sulfur about the size of a pea. Ignite it and lower 
the spoon into a bottle of oxygen. Note the bright 
blue flame and how much more brilliant the combustion 
is in pure oxygen than it is in air. Cautiously smell of 
the gas formed in the bottle. It is sulfur dioxide so 
much used for fumigation. 

The above experiments are examples of rapid com¬ 
bustion, but slow oxidation unaccompanied by light is 
taking place about us all the while. The heat of your 
body is being maintained by oxidation. All forms of 
decay, the drying of paint, the rusting of iron, the 
corrosion of metals, the bleaching of colored fabrics, 
the changing of cider to vinegar, and the antiseptic 
action of hydrogen peroxide are all examples of 
oxidation. 

Spontaneous Combustion.—Fires frequently start 
without any apparent cause. Wet hay in a mow, piles 
of coal dust, heaps of oily waste, rags saturated with 
paint or turpentine, and substances with a great affinity 



46 The Boys’ Own Book of Science 

for oxygen take fire spontaneously. A painter once 
told me that an oily rag, which he had stuffed into his 
pocket, took fire and burned his leg. I once had a 
quite serious fire in my laboratory from the spon¬ 
taneous combustion of sticks of yellow phosphorus, 
which had become exposed to the air. 

To illustrate this action place a few teaspoonfuls of 
carbon disulfide in a small glass-stoppered bottle and 
drop into it a piece of yellow phosphorus about the 
size of a pea. The phosphorus will quickly dissolve 
in the liquid. 

Two Cautions: Keep carbon disulfide away from a 
flame. Always cut yellow phosphorus in a basin under 
water f always keep it covered with water, and never 
touch it with the fingers except under water. 

If you should ever get a phosphorus burn immedi¬ 
ately apply a solution of potassium permanganate and 
continue to apply it at frequent intervals until the burn 
is healed. 

Now to come back to our illustration of spontaneous 
combustion, pour a little of the solution of phosphorus 
in carbon disulfide upon a piece of absorbent paper 
such as a filter paper and, holding it with pincers or 
tongs, wave it back and forth through the air. In a 
few moments the paper will take fire. What has hap¬ 
pened? Simply this—the carbon disulfide has evapor¬ 
ated leaving a finely divided layer of phosphorus on 
the paper. The phosphorus immediately begins to 
unite with the oxygen of the air and as it does so 
generates enough heat to bring it to its kindling tern- 



Oxygen and Hydrogen 47 

perature. When this point is reached nothing can 
prevent it from bursting into flame. 

In this experiment be very careful not to get any of 
the solution on your hands or clothes. 

How Gasoline Explodes.—Find a molasses can 
with a tight fitting cover. In the side and near the 
top punch a hole about a half inch in diameter. Place 
the can on a ring-stand. Set under it a candle and at 
the side a tall candle so that the top of it will come 
just under the hole that you have made. Now put 
six drops of gasoline or ether in the can and fit the 
cover on tightly. First light the candle at the side, 
then the one under the can, and step back. Soon an 
explosion will occur. 

As the gasoline vaporizes and mixes with the air an 
explosive mixture fills the can, which is ignited by the 
candle at the side. 

How Illuminating Gas Explodes.—In the top of 
another quart-size molasses can punch a hole about 
three-eighths of an inch in diameter. Make a second 
hole of the same size and near the bottom of the can. 
Through the hole at the bottom thrust a rubber tube 
connected to a gas jet. Allow the gas to run for about 
20 to 30 seconds, filling the can. Then turn off the 
gas, quickly remove the tube, and light the gas at the 
hole in the top of the can. 

The flame will grow smaller and smaller, but do not 
think it has gone out. Keep away and presently an 
explosion will occur. As the light gas escapes at the 
top and burns, air enters through the hole in the side 




48 The Boys* Own Book of Science 

and, when the can has become full of an explosive mix¬ 
ture, the flame strikes down and ignites it. This is the 
cause of the striking back of a gas burner and the 
frequent explosions that occur wherever gas escapes. 

A Dust Explosion.—Obtain another can similar to 
the other two but somewhat larger if possible. Punch 
a round hole in the middle of the bottom of it and 
insert through this from the inside your funnel, push¬ 
ing the stem down so that it projects underneath. 
Attach to the stem a 2 or 3 foot length of rubber 
tubing. Rest the can upon a ring-stand support. 
Place inside the can beside the funnel a candle about an 
inch long and light it. Have at hand an ounce of 
lycopodium powder, which you will be able to obtain 
from a druggist, or thoroughly dried powdered char¬ 
coal. Raising the free end of the rubber tubing, so 
that the powder cannot run out, pour a teaspoonful 
of it into the funnel and press the cover tightly into 
place. Then taking the tube in your mouth blow 
into the can with a strong quick breath, being careful 
to keep back as far as possible. 

The explosion is due to the sudden ignition of the 
mixture of dry combustible dust and air. A chance 
spark or flame in a dusty grain elevator or in a plant 
for grinding materials such as paint pigments fre¬ 
quently cause explosions of great violence. 

Oxidation is one of the fundamental types of chemi- 
ical change. We shall run across it time and again in 
our work, and before long it will become as familiar as 
an old friend. 



Oxygen and Hydrogen 
Hydrogen 


49 


Hydrogen is quite as interesting an element as 
oxygen. It was discovered by Sir Henry Cavendish in 
1766, and its name, meaning “water former,” was 
given to it by Lavoisier. As a constituent of almost 
all living organisms, as well as water, it is of tre¬ 
mendous importance. It occurs also in petroleum, 
natural gas, and coal tar. Until displaced somewhat 
by helium, it was the chief gas used in filling balloons 
and airships. 

Preparation of Hydrogen.—Arrange your gas gen¬ 
erator and pneumatic trough exactly as you did in the 
experiment with nitric acid and copper rivets in the 
chapter on Chemical Magic. See Fig. 4. But this 
time place in the generator granulated zinc or sheet 
zinc cut into small squares. 

Upon this zinc you will pour dilute sulfuric acid, and 
I must tell you how to prepare this solution. First, 
always remember that sulfuric acid must be poured into 
water and never water into the acid. In as large a 
beaker as you have place 300 or 400 c. c. of water and 
pour into it slowly and with constant stirring with a 
glass rod one-sixth that volume of the strongest sul¬ 
furic acid. The solution will be quite hot and before 
you use it let it cool. Then pour it into a labeled glass- 
stoppered bottle. 

The gas will be collected over water, as oxygen was. 
Have everything in readiness and be sure that the 
joints in your generating apparatus are all perfectly 


50 The Boys’ Own Book of Science 

tight. Then pour a little of the acid onto the zinc, 
enough just to cover it well, and take care to have the 
thistle tube dip beneath the surface of the acid. Keep 
your Bunsen burner at a safe distance from the appa¬ 
ratus. As soon as the acid comes in contact with the 
zinc, hydrogen gas will begin to be liberated, but do 
not collect it in the bottles just yet. The generator is 
at first full of air, and hydrogen and air form an ex¬ 
plosive mixture. Over the delivery tube hold an 
inverted test tube, and, since hydrogen is very light, 
it will rise and displace the air. Keeping the test tube 
mouth down bring it to a flame. A sharp report will 
be heard. This is because the air has not all been 
swept out of the generator. Repeat the operation, but 
do not bring the test tube immediately back to the 
delivery tube, for a flame plays about its mouth for a 
few moments, and, should you do so, the flame would 
strike back into your generator and the mixture would 
explode, driving the thistle tube to the ceiling. 

When the gas burns quietly in the test tube on pre¬ 
senting it to the flame, you may begin to collect the 
gas in the bottles. As the action slows down add 
more acid. Collect several bottles of the gas and 
leave them inverted over water until you are ready to 
use them. 

Combustibility of Hydrogen.—Holding an inverted 
bottle of hydrogen in the left hand, thrust up into it 
a lighted taper. Note that the hydrogen ignites at the 
mouth burning with an almost colorless flame. Also 
observe that the taper is extinguished as it is thrust 


Oxygen and Hydrogen 51 

into the gas, but relights as it is withdrawn from the 
bottle. This extinguishing and relighting of the taper 
may be repeated over and over, showing that hydrogen 
is combustible but does not support combustion. 

Hydrogen Lighter than Air.—Holding a bottle full 
of air in the left hand and a bottle of hydrogen in 
the right, slowly bring the bottle of hydrogen mouth 
upward beneath the bottle of air. Then present each 
bottle in succession to the flame. A sharp report will 
result in each case, showing that hydrogen must have 
risen upward into the second bottle. Were hydrogen 
a colored gas, this movement could be very readily 
seen. 

Affinity of Hydrogen for Oxygen.—In a dry glass 
test tube place some copper oxide, preferably of the 
wire form, and clamp the test tube to your ring-stand 
support so that the open end inclines slightly down¬ 
ward. Get your hydrogen generator into action again 
and be sure the gas is coming free from air. I hen 
pass the delivery tube nearly to the bottom of the test 
tube (Fig. 6). Let the gas run for a few moments to 
remove the air from the tube, and then heat the tube 
directly under the copper oxide, moving the flame back 
and forth as you do so. In a few moments steam 
will begin to issue from the tube and water will con¬ 
dense on the cooler portions. At the same time bright 
copper will form in the test tube. If you allow the 
hydrogen to continue to pass into the tube as the copper 
cools, it will remain bright. 

The alchemists would have said that this action 


52 The Boys’ Own Book of Science 

represents the transmutation of a black brittle sub¬ 
stance into copper. We now know that it is due to the 
union of hydrogen with the oxygen of the copper oxide. 
This kind of a chemical action we call reduction and 
hydrogen is a reducing agent. Oxidation and reduction 
are twin processes. They go hand in hand. We may 
have oxidation without reduction, hut not the reverse. 



Reduction of hot copper oxide to metallic copper with hydrogen. 

A Safe Explosion.—A perfectly safe explosion of 
hydrogen and oxygen and one that will afford you 
plenty of amusement may be easily carried out. Ob¬ 
tain from a druggist a bottle holding from one to two 
quarts and having a ground glass stopper. It will be 
necessary to cut the bottom off this bottle, but the 
following process will do it. Soak a hemp string in 
kerosene and draw it tightly about the bottle close to 




































Oxygen and Hydrogen 53 

the bottom. Light the string and when it is through 
burning thrust the bottle into cold water, the colder 
the better. I he bottom will usually crack off along 
the line of the string. 

Now using a deep jar for a pneumatic trough, fill the 
bottle with water and displace it with hydrogen from 
your generator. Have ready a one-hole rubber stop¬ 
per fitted with a short piece of glass tubing, as large in 
diameter as the stopper will permit of. When the 
bottle is full of hydrogen, rest it on two small blocks of 
wood so as to raise it about an inch from the table, 
quickly remove the glass stopper and insert in its place 
the rubber one. As you do so, direct your assistant 
to light the hydrogen escaping from the tube in the 
stopper. Then step back. 

The flame will grow small and may seem to disap¬ 
pear but do not become impatient. Presently it will 
strike down into the bottle and the explosive mixture 
will ignite with a very sharp report. As the hydrogen 
escapes, air enters from the bottom, forming the com¬ 
bustible mixture. 

Hydrogen from Water.—If your supply of chemi¬ 
cals contains metallic sodium, you should know that 
this substance must be kept under kerosene, for reasons 
that you will presently understand. It usually comes 
from the supply house in a sealed container. Open it 
and place the metal sodium in a bottle of kerosene. 

For this experiment cut off a piece about the size of 
a pea, pare off any yellow crust that may be on the 
outside, and wipe off the kerosene with filter paper. 


54 The Boys' Own Book of Science 

Wrap the sodium in a piece of sheet lead, leaving the 
tip exposed. Invert a test tube filled with water in 
your pneumatic trough and, grasping the sodium cap¬ 
sule with pincers, quickly thrust it beneath the mouth 
of the inverted tube. Immediately the sodium will 
begin to decompose the water and the test tube will 
fill with hydrogen. Present the tube to a flame and the 
gas will burn with a slight explosion. 

Hydrogen from Steam.—Some metals like sodium 



will liberate hydrogen from water at ordinary temper¬ 
atures. Others will do so only when heated. 

For this experiment obtain a 24-inch length of iron 
pipe. Fill it with small iron nails and mount the tube 
on two ring-stand supports. Place in each end either a 
one-hole cork stopper, or better a red rubber stopper, 
each stopper having inserted in it a short length of 
glass tubing. Connect to one end by means of a short 
piece of rubber tubing a flask containing a small quan¬ 
tity of water and mounted on a ring-stand over a Bun¬ 
sen burner. To the other end attach your delivery 











































Oxygen and Hydrogen 55 

tube and put in position the pneumatic trough and 
inverted bottles of water. In order to heat the iron 
pipe you will need what is called a 4-tube burner, that 
is, 4 Bunsen burners mounted so as to be fed from a 
single gas connection. You will find this piece of 
apparatus useful in other parts of the work too. (See 

Fig. 70. . • 

Now light the 4-tube burner and bring the iron pipe 
to a red heat. Then bring the water in the flask to a 
boil and pass steam over the red-hot iron. A very 
rapid stream of hydrogen will be liberated from the 
steam, which may be collected in the usual way. 

Many of you will not have the facilities for this 
experiment, but it will be interesting for those who 
have. 

Blowing Soap Bubbles with Hydrogen.—Between 
the delivery tube and the hydrogen generator place a 
short length of glass tubing containing a plug of cotton 
wool. To the end of the delivery tube attach a thistle 
tube or clay pipe. Prepare a strong solution of 
soap, as you have doubtless done many times before, 
but put into it this time a considerable quantity of 
glycerin. 

Now put the generator into action by pouring dilute 
sulfuric acid onto the zinc. Before you blow any 
bubbles test the gas to be sure that it burns quietly and 
is free from air. Dip the thistle tube into the soap 
solution and then almost immediately direct it upward. 
As the bubble increases in size give the tube a slight 
twist and it will release itself, rising rapidly to the 


56 The Boys’ Own Book of Science 

ceiling. It will also be interesting to light these bub¬ 
bles as they are released. 

Similar bubbles may also be blown with ordinary 
illuminating gas. 

What Forms When Hydrogen Burns?—Probably 
you have discovered the answer to this question al¬ 
ready, but to confirm it thrust the delivery tube of your 
generator into a dry test tube held mouth downward. 
After the hydrogen has had time to drive out the air, 
hold the tube to the flame and note that as the hydro¬ 
gen burns a film of moisture covers the sides of the 
tube. Water is the product. 



Chapter 7 

SIR HENRY CAVENDISH 

S ir Henry Cavendish was one of the queerest 
scientists who ever lived. He was one of the 
wealthiest men in England, but he cared nothing for 
his money. His sole pleasure in life came from experi¬ 
menting. And probably no man of his time was more 
expert as a glass-blower and an analyst than he. He 
did remarkably accurate work for those days, but it 
was entirely for his own satisfaction. He did not 
want anyone else to know about it. Now, we should 
call him selfish and eccentric. 

But we remember Cavendish chiefly for his dis¬ 
covery of the element hydrogen. Hydrogen, is the 
lightest known substance. It is the gas with which we 
fill balloons and airships. And shortly after Caven¬ 
dish’s discovery it was used to lift into the air some 
of the first balloons. Cavendish found that this gas 
burns with a very hot flame and in doing so produces 
water. Because it all seemed to disappear on burning, 
he called it pure phlogiston. And although he lived at 
the time of Priestley, Lavoisier, and Scheele, Caven¬ 
dish never accepted the new explanation of combustion. 
He clung to a belief in some sort of fire-stuff that dis¬ 
appeared on burning. 


57 


58 The Boy’s Own Book of Science 

After a time, in spite of all Cavendish’s opposition, 
the knowledge of his discoveries became known to 
other scientists. Then they sought to honor him. But 
Cavendish would have none of it. On one occasion 
he fled precipitately from the back door of the banquet 
hall and left those who had gathered to do him honor 
to go on without his presence. Even in death he sav¬ 
agely dismissed his servant that he might die alone. 
But although this old chap was exceedingly unlikable in 
his disposition, we must honor him today because of his 
great discoveries. 


Chapter 8 

THE ATMOSPHERE 

W E live at the bottom of a great ocean. It is as 
truly an ocean as are the immense bodies of 
water that bathe the continents. And we are as un¬ 
easy out of it as a fish out of water. In fact we cannot 
live without it. The air forms a very interesting 
subject for study. Possibly we may learn some things 
about it that you do not already know. Let us see. 

Does the Air Have Weight?—Place in one side of 
your hornpan balance a burned-out electric lamp. Just 
exactly counterpoise it by placing lead shot and bits of 
paper in the other pan. Then light your Bunsen 
burner and adjust the flame so that it is about an inch 
and a half high. (Of course an alcohol lamp may 
always be substituted for a Bunsen burner.) Holding 
the lamp close to one side of the flame, with your blow¬ 
pipe direct the flame against the glass. In a few mo¬ 
ments the glass softens and a hole is forced through 
it. You will also hear a sound like the escape of air 
through a small opening. 

Now place the lamp back in the balance pan. Note 
the increase in weight. An electric lamp bulb contains 
a vacuum, and, when you make a hole and admit air, 
the vacuum is destroyed and the bulb gains in weight. 

59 


60 The Boys’ Own Book of Science 

You may also prove this fact that air has weight 
with a football bladder. Attach it to one side of the 
balance and counterpoise it with lead shot on the other 
side. Then blow the bladder up and attach it to the 
balance again, using the same amount of string to 
fasten it that you did the first time. Since the quan¬ 
tity of air weighed in this experiment is much greater 
than in the other, the weight change will be much more 
pronounced. 

Presence of Oxygen in Air.—Of course the fact 
that substances burn in air would seem to indicate that 
air contains oxygen, but we need better proof. Obtain 
a quart fruit jar with a tight-fitting top of the clamp¬ 
fastening type. Observing the precautions about the 
use of yellow phosphorus, cut a piece under water about 
the size of a pea, wipe it very gently with a filter paper, 
being careful not to touch it with the fingers, and place 
it in your porcelain crucible set upon the upturned 
cover of the fruit jar. Have the jar fitted in advance 
with two new rubber rings well greased on both sides. 
Invert the jar over the cover and clamp it securely into 
place. Keeping the jar still inverted immerse the end 
containing the phosphorus in a basin of hot water for a 
few minutes. Presently the phosphorus reaches its 
kindling temperature and begins to burn, forming a 
dense white cloud inside the jar. 

After the action has stopped and the jar has cooled 
for fifteen minutes, thrust the end containing the cru¬ 
cible into a basin of cold water. Unfasten and pry 
off the top being careful to keep that end of the jar all 



The Atmosphere 


61 

the while immersed. As the top is removed, water 
will rise in the jar. Why? 

Slip a glass plate under the mouth of the jar and 
quickly invert it upon the table, keeping the water in 
the jar. Shake the water about gently so as to dissolve 
the white substance formed in the combustion. Thrust 
a burning splint into the air remaining in the jar. 
Note that the air no longer supports combustion. It 
must have lost something. 

Now pour into the water in the jar blue litmus solu¬ 
tion. The red color appearing shows the presence of 
an acid. Neither the air nor the water contained an 
acid at the start. It must have come from the change. 
Chemists know that this new compound is phosphoric 
acid and that it contains oxygen. Therefore the oxy¬ 
gen must have come from the air. 

There is another and simpler way of demonstrating 
the presence of oxygen in the air and one that you will 
understand more easily. Fill your porcelain crucible 
with short lengths of about No. 22 copper wire. Using 
the ring-stand support and a clay triangle (see Forms 
of Apparatus) place the crucible over the flame and 
gradually heat it to as high a temperature as possible. 
Occasionally stir the wire so as to bring all of the 
pieces in contact with the air. After about 30 minutes 
turn off the flame and allow the crucible to cool. The 
copper is no longer bright and flexible but black and 
brittle. It has undergone some chemical change. 
Let us discover w r hat it is. 

Place some of the new copper compound in a test 


62 The Boys' Own Book of Science 

tube clamped to a ring-stand, just as you arranged the 
apparatus in the reduction experiment with hydrogen. 
Set up your hydrogen generator and with zinc and 
sulfuric acid get it into action. Always remember to 
use dilute sulfuric acid, and I will tell you the secret of 
starting the action when the gas is slow in coming. 
Add through the thistle tube a few c. c. of copper 
sulfate solution. It will work like magic. 

When you have tested the hydrogen and found that 
it is free from air, that is, a test tube of it burns quietly 
without explosion, heat the test tube containing the 
copper compound and thrust the delivery tube up into 
it. In a few moments steam and water will come from 
the tube and bright copper will be left. 

Now must we not conclude that the new copper sub¬ 
stance contained oxygen? And from where did it get 
the oxygen, if not from the air? I think this proof 
will afford you considerable satisfaction. The expla- 
• nation looks simple now, but a century and a half ago 
it would have been a profound mystery. 

Another New Substance.—In this experiment with 
hydrogen and in the preceding ones, you must have 
noticed that the zinc disappears and the acid is used 
up. Your generator is not a perpetual motion ma¬ 
chine. It will not go forever. To prove that a new 
substance forms in the generator, filter some of its 
contents into your evaporating dish or onto a watch 
glass. Evaporate this solution over steam. This can 
be done by resting the dish or watch glass on the top 
of a “lipped” beaker containing water and mounted 


The Atmosphere 63 

over your burner (big. 8). As the water boils, the 
escaping steam will evaporate the solution to dryness. 
In this way you will find that a new compound forms in 
the generator. It is a white substance called zinc 
sulfate. 



Figure 8. 

A water bath for evaporating by steam. 


Carbon Dioxide.—You have often heard of carbon 
dioxide. The gas that frequently escapes from your 
stomach after drinking soda water is carbon dioxide. 
It is generated in processes of fermentation and decay. 
It is produced by yeast and baking powders in bread 
making and causes the bread to rise. It issues from 
the earth and is a product of important chemical 
changes. 

























64 The Boys’ Own Book of Science 

Is carbon dioxide present in the air?—Set a small 
beaker of limewater aside for a few hours. A white 
crust will form on the surface. With a bicycle pump 
force air through a tall cylinder or deep bottle of 
limewater for 20 minutes. Note the milky appearance 
of the limewater. As we shall see, this turning of 
limewater milky is a test for carbon dioxide. 

Preparation of Carbon Dioxide.—Place in your 
hydrogen generator some lumps of marble and arrange 
it just as you would for the preparation and collection 
of hydrogen. Being sure of course that the thistle 
tube reaches to the bottom of the bottle, pour through 
it upon the marble just enough water to cover the 
pieces and then add strong hydrochloric acid. Imme¬ 
diately a vigorous action will be set up and a rapid 
stream of gas will escape through the delivery tube, 
which may be collected over water in the usual way. 
Collect a number of bottles of the gas. It is carbon 
dioxide. 

Slipping a glass plate beneath the mouth of one 
bottle invert it upon the table. Pour into it a little 
limewater and shake. You will observe the same milky 
appearance obtained from pumping air through lime- 
water, except that- it is much deeper. 

Pour another bottle of the gas downward upon a 
lighted candle. By this experiment you prove that the 
gas is heavy and that it does not support combustion. 
Into another bottle thrust a burning splint. Again 
you obtain more proof of the character of this gas. 

Again start the action in the generator and pass the 




Generating carbon dioxide and collecting it over water. 




65 









The Atmosphere 67 

gas through blue litmus by dipping the delivery tube 
into some of the solution placed in a test tube. What 
does the color change show you about this gas? It is 
sometimes called carbonic acid gas. With water it 
gives the acid. Soda water is nothing but this gas 
dissolved in water under pressure. 

What are the causes of carbon dioxide in the air?— 
Through a glass tube having about an inch of the upper 
end bent slightly, bubble your breath through a little 
limewater in the bottom of a test tube. The tell-tale 
color denotes the presence of the gas. Respiration is 
then one source of carbon dioxide in the air. 

Lower a burning splint into a bottle of air. After 
a few moments withdraw it and pour limewater into 
the bottle. Shake the contents and note the evidence 
of carbon dioxide. Combustion is another source. 

By means of a wire attached to a lighted candle 
lower it into a quart bottle and cover the bottle tightly 
with a glass plate. Note how long the candle con¬ 
tinues to burn. 

Then fill the same bottle with water and invert it in 
your pneumatic trough or in a basin of water. 
Through a rubber tube dipping beneath the slightly 
upturned mouth of the bottle, blow into the bottle and 
with repeated breaths fill it with air from your lungs. 
Remove the bottle and lower into it a lighted candle, 
covering it as before with a glass plate. Again note 
the length of time the candle burns. What difference 
is there between fresh air and air expelled from the 
lungs ? 


68 


The Boys Own Book of Science 

Carbon dioxide is not a poison. Its presence in the 
air is sometimes an indication of the state of purity of 
the air, but in itself it is not harmful. On the other 
hand it has a number of important uses. Plants 
breathe it. It is a valuable fire extinguisher. When 
great clouds of it are produced by smudge pots and 
made to hover over the orchards of the West it pre¬ 
vents frosts and saves millions of dollars’ worth of 
fruit. Without it you would be deprived of the pleas¬ 
ures of soda water. 

Moisture in the Air.—In a bright metal cup place a 
little ether and blow into it through a glass tube. In 
a few moments a film of moisture will appear on the 
outside of the cup. From where did it come? Evap¬ 
oration of course produces cold, as we say, but it more 
properly absorbs heat. If it did not, evaporation 
would not take place. This heat comes from the air 
and quickly cools it to its dew point, the temperature 
at which condensation of moisture begins. 

If you have no ether, stir into some water placed in 
the cup a little cracked ice. This will also precipitate 
moisture on the outside of the cup. 

Your breath is constantly adding moisture to the 
air. Confirm it by breathing onto a cold window pane. 
Another source of moisture is combustion. Place your 
wash bottle full of cold water but dry on the outside 
on the ring-stand and light under it the Bunsen burner. 
Immediately a film of moisture will spread over the 
flask and often drops of water will run down its sides. 
From where does it come? At first this always 


The Atmosphere 69 

seems a perplexing problem. But when we re¬ 
member that a large percentage of illuminating 
gas or alcohol, if you use an alcohol lamp, is hydro¬ 
gen, which produces water upon burning, the answer 
is simple. 

Nitrogen in the Air.—Although nearly four-fifths 
of the air is nitrogen, this gas by itself is uninteresting. 
There is nothing we can do with it. It does not enter 
readily into combination with other elements. After 
we had removed the oxygen from the air with phos¬ 
phorus, you will recall that we thrust a burning splint 
into the remaining gas, but nothing happened, except 
that the splint went out. This gas was nitrogen and 
we learned that it neither burns nor supports combus¬ 
tion. But in its compounds nitrogen is a most fasci¬ 
nating element. Because of its weak chemical attrac¬ 
tion for other elements, it plays the leading role in 
the destructive power of high explosives. And its 
compounds have many other uses. One of the three 
chief kinds of foods must contain nitrogen. We shall 
run across it again a number of times before we are 
through with this work. 

Of course the air also contains about one per cent 
of the so-called rare elements, discovered by Sir Wil¬ 
liam Ramsay, and like nitrogen exceedingly inactive, 
so much so that they form no compounds at all. The 
most interesting one of them is helium, which is 
being used now as a substitute for hydrogen in filling 
airships. It is not quite as light as hydrogen, but it 
will not burn, and that avoids the frightful accidents 


70 The Boys’ Own Book of Science 

that sometimes occur when a spark from the motor 
pierces the gas bag. 

I am sure you will agree now that the atmosphere 
possesses much of genuine chemical interest. 


Chapter 9 

ANTOINE LAURENT LAVOISIER 


I N Lavoisier, a brilliant French chemist, we have 
another who at an early age established a well 
equipped private laboratory and turned his attention 
to science. That was the day of the home-laboratory 
worker. Lavoisier was born in 1743, the son of 
wealthy parents. He w T as able to put into his labora¬ 
tory everything that science and money could provide. 
But best of all he had a keen mind and a wonderful 
ability to interpret, or explain, the experimental facts 
which he observed. 

Scientists in those days had a very queer notion 
of just what happens when a substance burns. And 
if we were not the heirs of a century and a half of 
chemical investigation, we would still have the same 
strange idea. Maybe you do not know the cause of 
burnmg even yet. We call it combustion now. Up 
to the time of Lavoisier chemists supposed that in com¬ 
bustion an imaginary substance called “phlogiston >} is 
given off. What more natural, for something surely 
disappears? Coal for instance seems to be almost en¬ 
tirely consumed. But Lavoisier attacked this problem 
with a balance. He weighed everything entering into 
the chemical change and all the products. Nothing 


72 The Boys Own Book of Science 

escaped him. And he found that when a substance is 
heated or burned in the air the products of the change 
weigh more than the original substance itself. Even 
though a candle seems to disappear, the products of its 
combustion weigh more than the candle did itself. 
Clearly something from the air must unite with the 
candle. But what this something might be puzzled 
Lavoisier. He performed many experiments with the 
balance and always obtained similar results. 

Then one day Lavoisier learned of Priestley’s dis¬ 
covery of oxygen; although it was not called oxygen 
then, but “dephlogisticated air.” All gases were called 
“airs” in those days. And this bit of scientific news 
from across the Channel gave Lavoisier just the clew 
he needed for the explanation of combustion. He 
saw at once that oxygen is the element in the air that 
enters into combination when a substance burns. He 
also showed that the rusting of iron and many other 
chemical changes are due to the union of substances 
with this newly found element in the air, for Priestley 
and Scheele had shown that it exists in the atmosphere 
as well as in many chemical compounds. 

Because Lavoisier believed oxygen a necessary con¬ 
stituent of all acids, he gave it its name, which means 
“acid-former.” We now know this idea to be incor¬ 
rect, but the name will always remain. Lavoisier lost 
his life in the French Revolution and science thereby 
one of its most distinguished men. 


Chapter io 


ACIDS, BASES, AND SALTS 

A CIDS, bases , and salts are the three fundamental 
types of compounds with which chemistry has to 
deal. Without knowing it you are already familiar 
with many of these substances. One of the chief char¬ 
acteristics of an acid is its sour taste. You know the 
sour taste of vinegar, lemons, other citrus fruits, and 
plain soda water. You have drunk volumes of car¬ 
bonic acid in soda water, but fortunately it is a weak 
acid and it also decomposes in your stomach into two 
harmless products. Ammonia, lye, and limewater are 
bases. And ordinary table salt, borax, washing soda, 
cream of tartar, baking soda, and blue vitriol are com¬ 
mon salts. 

There is a very close relationship between these sub¬ 
stances, as we shall see. In order to test their proper¬ 
ties you will need two or three solutions of indicators. 
Litmus, methyl orange, and phenolphthalein are the 
three most common indicators. The first comes in the 
form of small cubes, and the other two as powders. 
To prepare litmus solution place a small handful of 
the cubes in a beaker, add 300 or 400 c.c. of water, 
and bring the mixture to a boil. Allow it to cool and 

73 


74 


The Boys Own Book of Science 

pour the clear solution into a stoppered bottle. Dis¬ 
solve a small pinch of methyl orange in a little de¬ 
natured alcohol and dilute with a considerable volume 
of water. Prepare phenolphthalein solution in the 
same way but do not add water. 

Now acids and bases give characteristic colors with 
these indicators. You have observed the changing 
colors of the leaves in autumn; they are due to the 
formation of acids in the sap of the tree. 

Color Effects of Acids and Bases.—Place a row of 
8 small beakers or tumblers on your table. In every 
other beaker place an acid, using hydrochloric, nitric, 
sulfuric, and acetic. Only a very little of each will be 
required. In the remaining beakers place solutions of 
sodium and potassium hydroxides, ammonia water, and 
limewater. 

(The sodium and potassium hydroxide solutions 
may be prepared by dissolving a 3-inch stick of each 
in 200 c.c. of water. Household ammonia will always 
be at hand, and limewater is prepared by shaking a 
handful of slaked lime with a quart of water and allow¬ 
ing the mixture to stand for a few hours. Then pour 
off the clear liquid.) 

Now dilute the contents of each beaker with a little 
water from your wash bottle. (See Forms of Ap¬ 
paratus in first chapter.) Have at hand three small 
bottles containing the indicators. By means of a 
medicine dropper introduce one or two drops of litmus 
into each beaker. Note the characteristic red ob¬ 
tained with each acid and the blue with each base. 


Acids, Bases, and Salts 75 

Litmus is the indicator commonly used to test for an 
acid or a base. 

\ ou will find it interesting to pour the contents of 
one beaker into that of another. In some instances 
the blue will predominate, in others the red. Why? 

Rinse out the beakers thoroughly and arrange 
another series of acids and bases just as before. But 
this time use methyl orange indicator, introducing it 
with a fresh dropper. What colors do you obtain 
now ? 

Again repeat the experiment, using phenolphthalein 
indicator. You will observe that only the basic solu¬ 
tions give a color in this case. 

Testing Common Things.—Squeeze out and filter 
into clean test tubes the juice of lemons, grape-fruit, 
orange, and a sour apple. In other test tubes dissolve 
with a little water small quantities of lye, baking soda, 
borax, and washing soda. Then in succession divide 
each solution into three portions and test them with 
the above indicators. Although the three last sub¬ 
stances taken are salts, for reasons that you would not 
now understand, they give basic, or alkaline, reactions. 

Shake some wood ashes in a test tube with water, let 
them stand for a while, filter and test for acid and base. 
Ashes are used to destroy the acid condition of old soil, 
or to sweeten the soil, as the farmer says. 

Dissolve soap in water and test the solution with 
phenolphthalein. The cleansing action of soap is 
partly due to its alkaline reaction. 

Preparing a Salt.—A salt is formed by the chemi- 


76 The Boys’ Own Book of Science 

cal union of an acid and a base, and the process is 
called neutralization . 

Dissolve a piece of sodium hydroxide about as big 
as a pea in a test tube of water and pour half of the 
solution into an evaporating dish. Prepare a dilute 
solution of hydrochloric acid by mixing 10 c.c. of the 
strongest acid you have with 100 c.c. of water. Nearly 
fill a test tube with this acid and insert in the mouth of 
the test tube a cork having two small notches cut in 
opposite sides of it. This will afford you a good 
dropper. 

The most convenient indicator for general use in 
your laboratory will be litmus in the form of red and 
blue litmus paper. This can be readily obtained, and 
you should cut it into small narrow strips. 

On a small glass plate beside your evaporating dish 
containing the sodium hydroxide solution place a strip 
of each kind of paper. Prepare a glass stirring rod by 
fusing in the flame the ends of a piece of tubing. Then 
add the acid to the base with constant stirring, a few 
drops at a time and after each addition touch the end 
of the stirring rod to each kind of paper. At first 
the red paper will be turned blue, but after a time you 
will reach a point where the reverse change occurs. 
This means that you have over-stepped the end-point, 
or neutral point. The solution is now slightly acid. 
Therefore add a few drops of base from the tube 
in which you prepared it and bring the solution back 
to a faintly alkaline condition. You will then have 
reached a point where a single drop of acid will cause 


Acids, Bases f and Salts 77 

the solution to turn blue litmus red, and a single drop 
of base will cause it to turn red litmus blue. The acid 
and base have now neutralized each other and you 
have in solution a salt. Dip the glass rod into the 
solution and touch it to your tongue. What is the 
salt ? 

Now evaporate the solution to dryness, using a small 
flame at the end so as to avoid spattering. You have 
prepared ordinary table salt, or sodium chloride, and 
if your chemicals were pure, the salt will be chemically 
pure. 

There are many salts, and with any other acid and 
base in like manner you may prepare others. 

Titration.—The process of neutralization is of 
great importance in analytical work. As carried out 
there, it is called titration. While we shall do no 
analytical work at this time, it will be interesting to 
learn the process. 

For this work you will need two burettes holding 
50 c.c. each. (See Forms of Apparatus.) In one, place 
a dilute solution of hydrochloric acid, and in the other, 
a dilute solution of sodium hydroxide. Mount these 
burettes on a ring-stand support by means of clamps 
(Fig. 9). Have at hand a small beaker, a stirring 
rod, and phenolphthalein indicator. On the table 
under each burette place a square of white paper. 
Place the beaker under the sodium hydroxide burette 
and run out about 10 c.c. of the base, allowing it to 
run down the stirring rod. Remove the drop clinging 
to the tip of the burette with your stirring rod and 



78 The Boys’ Own Book of Science 

wash down the rod and the drops spattered on the 
inside of the beaker with a stream of water from your 
wash bottle. 

Now add a drop of phenolphthalein to the contents 
of the beaker and run in acid, at first rapidly and then 



Burettes set up for determining the strength of an acid or a base by titration. 


drop by drop, until the pink color produced by the 
indicator is just destroyed. Again remove that last 
drop clinging to the burette and rinse down the rod 
and sides of the beaker. If the work has been done 
carefully, you have now reached a point where a single 
































Determining the strength of an acid by titration. 


79 
















Acids, Bases, and Salts 81 

drop of either solution will produce the color change. 
This is the end-point. Taste of the neutralized solu¬ 
tion. If you like, evaporate it, as before. 

You are now getting to be a real chemist, for these 
are real chemical processes. An interesting additional 
experiment will be the titration of “white'’ vinegar 
with sodium hydroxide as the base. Ammonia and 
hydrochloric acid may be titrated, using either litmus 
or methyl orange as the indicator. 

Preparation of Hydrochloric Acid.—As we have 
seen an acid combined with a base produces a salt. 
Therefore we ought to be able to obtain an acid from 
its salt, and that is exactly the method that we shall 
employ. 

Mount a 500 c.c. flask on your ring-stand and fit it 
with a 2-hole stopper carrying a thistle tube and bent 
angle tube. Attach the delivery tube and pass it 
through a cardboard cover nearly to the bottom of the 
collecting bottle (Fig. 10). Place three or four table¬ 
spoonfuls of ordinary table salt in the flask and moisten 
it with a little water. Then add about 20 c.c. of the 
strongest sulfuric acid through the thistle tube and 
heat the flask gently with the flame. Be sure you have 
an asbestos gauze under the flask, and if possible place 
the apparatus in a good draft. 

Now hydrochloric acid is a gas dissolved in water, 
and what you will obtain here is the gas. It will be¬ 
gin to come off quickly, and, as the bottle fills and the 
gas escapes into the air, dense white fumes will appear. 
This is because of the great affinity of this gas for 


82 


The Boys’ Own Book of Science 

water. It condenses it from the air forming little 
droplets of hydrochloric acid solution. When the bottle 
begins to fume around the mouth, remove the delivery 
tube and hold it just above about a half-inch depth 



Figure io. 

Apparatus for the preparation of hydrochloric acid. 


of water in the bottom of another bottle. Looking 
through the solution toward the light, note the oily 
appearance of the water, as the gas dissolves. 

Quickly invert the bottle of gas, which you have pre¬ 
pared, in a basin of water colored with blue litmus. 
If the bottle is full of the hydrochloric acid gas, the 




































Acids, Bases, and Salts 83 

water will rise into it with a rush and at the same time 
turn the blue litmus red. Hydrochloric acid is the 
second most soluble gas known. 

Pour a little strong ammonia water into a beaker 
and bring near to it the delivery tube of the generator. 
If the hydrochloric acid is still coming, dense white 
fumes will form. The hydrochloric acid and ammonia 
gases unite to form ammonium chloride, or sal 
ammoniac. 

Test a little of the acid solution that you have pre¬ 
pared with litmus. Pour a little of it onto some mag¬ 
nesium ribbon in a test tube. Note the rapid action, 
and bring the mouth of the test tube near the flame. 
The combustion which you obtain shows the presence 
of hydrogen. Repeat using zinc or iron nails in place 
of magnesium. 

You have now established two of the fundamental 
properties of an acid. It changes blue litmus red, and 
liberates hydrogen with a metal. 

Preparation of Nitric Acid.—Nitric acid is a very 
active and interesting compound. It is one of the 
most powerful oxidizing agents known to chemistry 
and of great importance in the manufacture of ex¬ 
plosives. Unlike hydrochloric acid, it is a liquid and 
may be distilled from a mixture of saltpeter and sul¬ 
furic acid. 

Place in your glass-stoppered retort (see Forms of 
Apparatus) two tablespoonfuls of either sodium or 
potassium nitrate. These are salts of nitric acid, and 
just as we obtained hydrochloric acid from one of its 



84 The Boys Own Book of Science 

salts, so we shall employ the same method here. To 
introduce the salt into the retort place it upon a square 
of smooth paper and holding the retort in the left hand 
and the paper in the right slide the salt in. Then 
through a funnel pour on the nitrate about 15 c.c. of 



Distilling nitric acid from a mixture of sulfuric acid and Chili saltpeter. 

Figure ii. 

strong sulfuric acid. Mount the retort on a ring-stand 
and thrust the neck into a flask resting in a jar of cold 
water (Fig. 11). Gently heat the retort and very 
soon the vapor of nitric acid will appear and begin 
to condense in the neck of the retort and run down 
into the flask. During the process rotate the flask so 
as to cool it more and make it a better condenser for 
the acid. Continue the action as long as acid distils 

























Acids, Bases, and Salts 85 

over. Then allow the contents of the retort to cool, 
add water and let it stand until the salt cake left in 
the retort has dissolved. But do not add water until 
the contents of the retort have cooled. 

Oxidizing Action of Nitric Acid.—Into a test tube 
pour 2 c.c. of the strong nitric acid which you have 
just prepared. Stuff into the tube just above the acid 
a plug of excelsior and heat both the acid and the 
the excelsior in the flame. A very brilliant combus¬ 
tion will occur. The nitric acid decomposes liberating 
oxygen, which unites with the combustible excelsior. 

In your evaporating dish heat some sawdust until it 
just begins to char. Then pour upon it 3 c.c. of the 
nitric acid. A very vigorous combustion is set up. 

A mixture of sugar and nitric acid warmed in a 
test tube produces a similar result. 

On the wire gauze of your tripod or ring-stand place 
a small beaker or Erlenmeyer flask containing a mix¬ 
ture of sodium nitrate and sulfuric acid. Heat this 
gently and by means of tongs thrust into the hot vapor 
of nitric acid, which soon escapes, a glowing splint. 
The splint will instantly ignite and burn brilliantly. 
As it does so, brown fumes of nitrogen peroxide will 
also appear. 

These experiments show the great oxidizing power 
of nitric acid and how unstable a compound it is. It 
is for this reason that this acid is used in the manu¬ 
facture of high explosives. 

Action of Nitric Acid on a Metal.—Pour 2 c.c. of 
the acid upon a copper rivet in a test tube. Add a 


86 The Boys' Own Book of Science 

drop or two of water and a most vigorous action will 
result, accompanied by dense brown fumes of nitrogen 
peroxide. Nitric acid, unlike sulfuric and hydrochloric, 
does not liberate hydrogen when acted upon by a 
metal. This is because the hydrogen is oxidized by 
the acid as fast as it forms. 

Preparation of a Base.—To a little ammonium chlo¬ 
ride (sal ammoniac) in a test tube add a few c.c. of 
sodium hydroxide solution and heat. Hold in the 
gas a piece of moist red litmus paper. It will be turned 
blue showing the presence of a base. Smell of the gas 
cautiously. What is it? 

Prepare a mixture of equal parts of sal ammoniac 
and dry slaked lime. Place it in a test tube fitted with 
a stopper and delivery tube exactly as you did in the 
preparation of oxygen. Clamp the tube to a ring- 
stand and thrust the delivery tube upward into an 
inverted bottle. The delivery tube should pass through 
a cardboard which acts as a cover for the bottle. Now 
heat the test tube gently along the whole length of 
the mixture, and the bottle will quickly fill with am¬ 
monia gas. Thrust the inverted bottle in a basin of 
water and note how rapidly the gas dissolves. If the 
water has been colored red with litmus to which a drop 
of sulfuric acid has been added, as the water rises in 
the inverted bottle, it will be turned blue by the action 
of the ammonia, which is a base. 

Sodium and potassium hydroxides, the two strong¬ 
est bases, may be prepared directly by the action of the 
metals upon water. The action in each case is vigorous 


Acids, Bases, and Salts 87 

with the liberation of hydrogen. In the case of 
potassium the hydrogen takes fire giving a lavender to 
violet colored flame. 

Sulfuric acid is one of the three most important 
raw materials of chemical manufacture. It is pro¬ 
duced in enormous quantities. There are two com¬ 
mercial processes, but each depends upon the oxida¬ 
tion of sulfur dioxide and the absorption of the product 
in water. 

You may prepare this acid by passing sulfur dioxide 
into hydrogen peroxide. In your hydrogen generator 
place 3 teaspoonfuls of sodium sulfite. Pass the de¬ 
livery tube to the bottom of a test tube half full of 
hydrogen peroxide. Through the thistle tube of the 
generator pour hydrochloric acid. The sulfur dioxide 
which is generated will unite with the hydrogen per¬ 
oxide to form sulfuric acid. Note that the test tube 
gets quite warm from the heat liberated in the re¬ 
action. Divide the solution into two portions. Test 
one with litmus. A decided acid reaction will be ob¬ 
tained. To the other portion add barium chloride 
solution and you will obtain a white precipitate which 
will not dissolve in hydrochloric acid. These tests 
prove that you have prepared sulfuric acid. 

Testing Soils.—Bring moist samples of various 
kinds of soil in contact with moist red and blue litmus 
paper. After a time examine them. Old soil will 
give an alkaline reaction. When you have found a 
soil that does this, mix a basin full of it with 20 to 25 
g. of well pulverized burned lime. Stir this thoroughly 



88 The Boys’ Own Book of Science 

and test again. Do you now understand why farmers 
use large quantities of lime on their plowed fields? 
Into another basin full of acid soil stir a handful of 
wood ashes. Again make the litmus test. Wood ashes 
contain potassium carbonate, a substance which like 
a base will neutralize an acid. In addition the element 
potassium is one of the three essential constituents of 
commercial fertilizers. 


Chapter ii 


THE EXAMINATION OF WATER 

W ATER will dissolve more substances than any 
other one liquid. Its purity is absolutely essen¬ 
tial to the health of people everywhere. It touches 
life in countless ways. We have seen that it is com¬ 
posed of hydrogen and oxygen. Chemically, it is a 
most interesting substance, and its study will afford 
us a great deal of real laboratory work. 

Natural water is never pure. In the chemical sense 
we mean by pure water, water free from organic and 
mineral matter. Water may be fit to drink and yet 
contain mineral matter in solution. Since water is 
the best solvent known, it is all the while taking into 
solution foreign matter. The purest water in nature 
is rain water, but even this contains gases washed from 
the atmosphere and it is discolored from running over 
dirty roofs. You do not need to be told that the water 
we drink is of the utmost importance. In many indus¬ 
tries, too, water must be selected with the greatest care. 
Iron in water is objectionable for dyeing, tanning, 
paper making, bleacheries, and laundries. Chlorides 
are harmful in the refining of sugar and the tanning 
of leather. Hard water cannot be used in laundries 

without softening, and it is the chief cause of boiler 

89 


90 The Boys' Own Book of Science 

scale. For drinking, water must be free from harmful 
bacteria and organic substances and not contain too 
much mineral matter. I think you already see that 
this examination of water is going to open up a fasci¬ 
nating field for the amateur chemist. 

First let us look into the matter of purifying water. 
[ here are two principal methods—filtration and dis- 



FlGURE 12. 

Simple filtration for separating a solid suspended in a liquid. 


filiation. Filtration removes sediment and may re¬ 
move organic matter. Distillation removes all soluble 
matter and of course destroys any bacteria that may 
be present. 

Filtration.—Stir a little soil into a beaker of water. 
Then fold a filter paper and fit it in your funnel placed 
on the ring-stand support. Pour the muddy water 
through the filter and catch the clear liquid that runs 






















Distillation of water. 


91 


















93 


The Examination of IVater 

through, called the filtrate f in another clean beaker 
(Fig. 12). This is the method always employed in 
the laboratory for the removal of suspended sediment. 

Prepare a solution of ordinary table salt and pass 
it through another filter. Taste of the filtrate. This 
sort of filtration, you see, does not remove dissolved 
mineral matter. Confirm this by filtering a solution 
of blue vitriol, but do not taste it. 

Filtering through Boneblack.—In a small beaker 
place 25 c.c. of cider vinegar and stir into it two tea¬ 
spoonfuls of boneblack, or animal charcoal. Heat the 
mixture nearly to boiling for a few moments. Then 
pour it through a fresh filter into a clean beaker. 
Note that the vinegar has been decolorized. 

Repeat this operation with a fairly strong solution 
of blue vitriol. This time the color remains. You 
have demonstrated a fact of considerable commercial 
importance, that boneblack will remove organic but 
not mineral coloring matter. In the refining of sugar 
boneblack filters are used to decolorize the syrup. 

Another Method for Removing Color.—Natural 
water is frequently highly colored from having passed 
through peat beds or masses of decaying vegetation. 
In the manufacture of paints and pigments, organic 
dyestuffs must be removed from solution. A gelati¬ 
nous substance known as aluminium hydroxide is very 
extensively employed in these decolorization processes. 
To learn the action of such a filter, prepare a dilute 
solution of ordinary alum by dissolving 5 g. of the 
salt in 250 c.c. of water. Also have at hand limewater, 



94 The Boys Own Book of Science 

made by shaking slaked lime with water in a stop¬ 
pered bottle and allowing the mixture to stand for 
several hours. Then pour off the clear liquid. To 
one-sixth of a test tube of the alum solution add twice 
that volume of limewater and warm gently over the 
flame. Note the white gelatinous precipitate that 
forms. A precipitate is an insoluble substance which 
is formed when two solutions are mixed. If ammonia 
water is substituted for the limewater, a heavier pre¬ 
cipitate may be obtained. 

To show how this precipitate may be used to re¬ 
move coloring matter prepare dilute solutions of some 
organic dyestuff. Logwood or alizarin are good for 
this purpose. Then to half a test tube of the alum 
solution add a little ammonia water, just enough to 
form a thin precipitate. Follow this with enough of 
the dyestuff to give a distinct color. Shake the mix¬ 
ture well and set the tube away. Within a short time 
you will note that the precipitate is settling and carry¬ 
ing down with it the coloring matter. After a time 
you will find a clear liquid above and a sediment of 
color-substance at the bottom. This color-substance 
is called a “lake,” and such lakes are employed very ex¬ 
tensively in the preparation of pigments. This gelat¬ 
inous precipitate, known chemically as aluminum 
hydroxide, is also used to absorb the coloring matter 
from water. 

A Sand Filter.—You may illustrate the action of 
aluminum hydroxide on water and also the efficiency 
of sand and rock in filtering natural water by making 


95 


The Examination of Water 

a sand filter. Obtain a bottle of either a half-gallon 
or gallon capacity. Cut off the bottom according to 
the directions already given in the chapter on hydro¬ 
gen and oxygen. Mount this, neck down, either on 
your ring-stand or on a support made by cutting a hole 
through the top of a box and knocking off one side. 
Fit into the neck of the bottle a rubber stopper carry¬ 



ing a short length of glass tubing to which you have 
attached a piece of rubber tubing and a pinch-clamp. 
In the bottom of this container place some clean gravel. 
Follow this with an inch layer of well washed sand. 
Then sprinkle in a very thin layer of powdered alum 
and slaked lime. Add alternately layers of sand and 
small amounts of alum and lime, until the bottle is 
nearly full (Fig. 13). Pour water through the filter 



















9 6 The Boys’ Own Book of Science 

and, if it is not at first clear, continue to do so until 
the filtrate is free from sediment. 

Now prepare several quarts of water colored with 
a small quantity of some dyestuff such as alizarin or 
magenta. The dyestuff may be dissolved in a little 
denatured alcohol, and only a few cubic centimeters of 
it will be required to give a deep color to a gallon of 
water. Pour this solution through your filter and 
draw it off by opening the pinch-clamp at the bottom. 
You will find that the water has been entirely freed 
from coloring matter. The alum and lime slowly 
unite to form the precipitate of aluminum hydroxide, 
and this together with the sand removes the organic 
matter. Such mechanical filters are used very much in 
the industries, and alum and lime are placed in city 
reservoirs to remove both sediment and organic color¬ 
ing matter. 

If possible, obtain a gallon of natural water con¬ 
taining both sediment and coloring matter and try the 
action of your filter upon it. Such a filter also removes 
bacteria. Do you not see why water from springs 
and deep artesian wells, which has seeped through 
many layers of sand and gravel, is pure? 

Distilled Water.—For many purposes water must 
be free from both organic and mineral matter. Fil¬ 
tered water is never free from dissolved mineral mat¬ 
ter. But for all work in exact chemical analysis, for 
storage batteries and the manufacture of ice this, too, 
must be removed. The only way to get this matter 
out is by distillation. In this process we boil the water 


The Examination of IVater 97 

and condense the steam. Nothing but the steam passes 
over. The mineral matter is left behind. 

A simple still may be made from a flask, a one-hole 
stopper, a bottle, a test tube, and a piece of bent tubing. 
(See Fig. 14.) The test tube surrounded by the 



Figure 14. 

Two set-ups for the distillation of water. 


cold water in the bottle will condense the steam. 
The cooling water must be changed frequently and the 
flame should not be large. 

When the still is ready, place in the distilling flask 
a solution of blue vitriol and light the burner. Let the 
water boil gently and soon you will notice the condensa¬ 
tion of steam in the cooled test tube. This water that 

























































98 The Boys' Own Book of Science 

distils over is called the “distillate,” and you will note 
that it is colorless. It is pure water. It contains 
neither mineral nor organic matter. Place a little of 
the water in your mouth. You may think that it tastes 
“flat,” but it is really tasteless. Pure water has no 
taste. This is the kind of water with which chemists 
do their work. 

Empty out the distilling flask and substitute for the 
blue vitriol a dilute solution of some dyestuff. As this 
distils over note that the liquid, which you collect, is 
colorless and tasteless. The dyestuff is an organic 
substance. 

To show how natural water may be purified, from 
a stagnant pool obtain a sample containing both sedi¬ 
ment and coloring matter. Filter it through the sand 
filter. It will come through free from sediment and 
color. But place a little of the filtrate on a watch 
glass and evaporate it over steam. As I have already 
told you, to do this place the watch glass on the top 
of a half-filled beaker of water and heat with the 
Bunsen flame. If there is no lip on the beaker, draw 
the watch glass slightly to one side so as to allow the 
steam to escape. As the water evaporates, you will 
observe a white residue on the watch glass. This is 
mineral matter which the sand filter could not remove. 

Now distil some of the water that passed through 
the filter and again evaporate a little of the distillate 
over steam. This time you find no residue. 

Your distillation experiments can be carried out on 
a much larger scale if you have a Liebig condenser, 


99 


The Examination of Water 

as shown at the left in Fig. 14. To use it you will need 
running water and a sink. If your laboratory does 
not contain them, possibly you could use the kitchen. 

The chemical purification of water for drinking 
purposes is also important. To destroy bacteria and 
organic matter the poisonous gas chlorine and the 
powerful oxidizing agent ozone are employed, besides 
aeration. In the latter process the water is thrown 
upward in a spray and mixed with the air which oxi¬ 
dizes the organic matter. These methods, you will 
be unable to demonstrate. 

Sanitary Examination of Water.—If you are to be 
a real chemist you must be able to determine whether 
water is pure and wholesome to drink. Has it suf¬ 
fered contamination from sewage, sinks, or products 
or organic decay? Is it free from an excessive quan¬ 
tity of mineral matter? Does it contain lead dissolved 
from the pipes through which it has passed? These 
and other questions you must be able to answer. 

Taking the sample is of the utmost importance. 
In doing so note the surroundings. Discover whether 
there is any possible source of contamination. Then 
be sure that the bottle in which you take the sample 
is chemically clean. Simply washing with soap and 
water is not sufficient. F’ill it a quarter full of strong 
sulfuric acid to which you have added a small quantity 
of potassium bichromate crystals. Let the solution 
stand for several hours, shaking at frequent intervals. 
Then pour the solution into a glass-stoppered bottle 
and preserve for future use. Rinse the bottle well. Fill 


> 1 
> > > 


IOO 


The Boys' Own Book of Science 

it with the water to be examined. T hrow this out 
and fill it again. Take the sample to the laboratory 
and begin its analysis at once. 

The amount of sediment in water, its color, and 
its odor are indications of its purity. Allow a test 
tube of the water to stand overnight, unless it is per¬ 
fectly clear. Pour off the liquid and if there is a resi¬ 
due examine it with a hand magnifier. If bits of hair 
or cotton and woolen fibers are present, they might 
indicate organic filth. To test the color, fill a long 
test tube with the water and stand it on a piece of 
white paper in front of a window giving a good light. 
Back of the tube place a piece of white paper extend¬ 
ing almost to the bottom. If on looking down into the 
tube, the water is transparent, or shows only a slight 
bluish tinge, the color is natural. If, however, there 
are tints of brown, yellow or green, the water may be 
polluted. To determine whether the water has odor, 
fill a flask half full and stopper it. Heat it until the 
glass feels thoroughly warm. Shake it, unstopper, and 
smell of the gas that has been driven from the water. 
Pure water will give no odor. If the odor is putrid, 
the presence of decaying organic matter is indicated, 
and it may be either of animal or vegetable origin. 

The total solids in water is another important item. 
By total solids is meant the residue of mineral and 
organic matter left upon evaporating water to dry¬ 
ness. To make a real determination of this, you must 
have a balance. A hornpan balance will do. Weigh 
in it your evaporating dish to the nearest milligram, 


IOI 


The Examination of Water 

that is, o.oo i g. Your set of weights should permit 
you to do this. Place in it ioo c.c. of the water, or 
half that amount if your dish is small. The water may 
be measured either with a graduate or a pipette. 
Evaporate this over a half-filled beaker of water to 
complete dryness. Then heat it over a very small 
flame for 30 minutes. When the dish has cooled so 
you can handle it, weigh it again. The increase 
in weight gives the total solids. If 100 c.c. were taken, 
the increase in weight in milligrams multiplied by 10 
will give you the number of parts per million of solids 
in the water. For drinking purposes this should not 
be over 600. 

The next step is to determine the presence of 
organic matter. To do this evaporate to dryness, as 
above, 50 c.c. of the sample in a porcelain dish. When 
dry, place the dish over a Bunsen burner and heat very 
gradually to a considerable temperature. If the resi¬ 
due chars and blackens, organic matter is present and 
at once indicates contamination. The organic matter 
in itself is not harmful, but it may be associated with 
disease-producing bacteria. 

Chlorine, in the free state, is a deadly poison. In 
the form of sodium chloride it is essential to life. Al¬ 
though chlorine in combined form is not harmful, 
natural water contains it in only very small quantities. 
If much is present, it usually means sewage contamina¬ 
tion. 

The qualitative test may be very simply made. Dis¬ 
solve a small crystal of silver nitrate in 10 c.c. of dis- 


102 


The Boys Own Book of Science 

tilled water. (A druggist will supply you with 
distilled water, or you may prepare it if you have a 
Liebig condenser.) Add a pinch of table salt to a 
half test tube full of tap water and then a few drops 
of the silver nitrate solution. A white precipitate of 
silver chloride will be obtained. This is the test for 
a chloride. Make a very dilute solution of the sodium 
chloride, not over a half dozen grains to a test tube 
of water, and repeat the test. This time you obtain 
only a cloudiness in the water, and yet it is probably 
deeper than what you will get with any natural water 
that is fit to drink. 

Now make the test on the sample of water which 
you are examining. Pure water should contain very 
little chloride. If the test gives more than a faint 
cloudiness, the water should be regarded with 
suspicion. There may be some perfectly harmless 
source of the chloride, such as a field fertilized with 
chloride of potash, and that is where a knowledge of 
the conditions surrounding the water supply is of the 
greatest importance. 

For those amateur chemists who have the equip¬ 
ment I shall describe the quantitative test for chlorine. 
For this determination you will need a standard solu¬ 
tion of silver nitrate. This is a solution prepared by 
dissolving exactly 2.394 g. of silver nitrate crystals in 
a liter of distilled water. A liter is 1000 c.c. Flalf 
or even a quarter of that volume will be sufficient. 
Suppose we prepare 250 c.c. by dissolving 0.599 g- of 
the silver salt in that volume of water. Mount on 


The Examination of Water 103 

your ring-stand support a burette and nearly fill it to 
the top graduation mark with the solution. 

To read a burette place your eye on a level with 
the surface of the liquid in it and take the reading 
from the lowest point of the curved surface, estimating 
the number to the nearest tenth of a c.c. The differ¬ 
ence between two successive readings will be the 
number of c.c. used. 

This will be another titration experiment and you 
will need an indicator. Prepare it by dissolving 5 g. 
of potassium chromate in 10 c.c. of water. To learn 
the effect of silver nitrate upon this, add 3 or 4 drops 
of the indicator to a little water in a beaker and run 
in from your burette a few drops of the standard 
solution. A red precipitate will form. Then prepare 
a very dilute solution of sodium chloride and add to 
it the indicator. As you run in the silver nitrate this 
time, note that white silver chloride at first forms, 
after which with continued addition of the standard 
solution the red precipitate appears. But this will not 
happen until all of the chloride has been precipitated. 

Now to make the real test, transfer to a small 
beaker 50 c.c. of the water to be examined and add 
to it 3 or 4 drops of the indicator. Place this on a 
white paper under the burette near a window giving 
good light. Record the reading of the burette and 
begin to add the standard silver nitrate solution a drop 
at a time, stirring after each addition with a clean glass 
rod, which must not be removed from the beaker. 
Continue this until a faint tinge of red appears. When 


104 The Boys’ Own Book of Science 

this happens you may know that the chloride has just 
all of it been precipitated. Take the final reading of 
the burette and subtract the first reading from it. 
Each cubic centimeter of silver nitrate used means io 
parts of chlorine per million parts of water. In the 
most exceptional cases there should never be more than 
50 parts per million, and usually the amount is less 
than 10. 

Nitrogen.—Another highly important indication of 
the fitness of water for drinking purposes is the pres¬ 
ence of nitrogen compounds. They may be found as 
ammonia, nitrites, or nitrates. Whenever nitrogen in 
any form is found in water, it means contamination 
from organic sources. The nitrogen itself is not harm¬ 
ful but with it will usually be found germs of disease. 

The tests for these substances are very delicate and 
they cannot be carried out in a room containing any 
ammonia bottles. 

To test for ammonia a solution know as Nessler’s 
Reagent will be required. Get your druggist to pre¬ 
pare a small bottle of it for you. It would be rather 
difficult for you to prepare it yourself. Place 50 c.c. 
of the water to be tested in a tall test tube and add 
to it from a pipette or a burette 2 c.c. of the reagent. 
After 5 minutes look down into the tube. A yellowish 
brown tinge proves the presence of ammonia. 

But ammonia may also be present in combined form 
and in that case the above test would not show it. To 
test for ammonia compounds prepare a solution con¬ 
sisting of 125 c.c. of distilled water, 25 g. of potas- 


The Examination of Water 105 

sium hydroxide, and 1 g. of potassium permanganate. 
Fill your distilling flask half full of the water to be 
tested and add to it 25 c.c of this solution. Into 
tall test tubes distil off successive portions of 50 c.c. 
each. Throw the first portion away, for the apparatus 
itself might have contained traces of ammonia com¬ 
pounds. I o each of the other portions add 2 c.c. of 
Nessler’s Reagent and at the end of 5 minutes ex¬ 
amine the color. A yellowish tinge tells the story. 

To detect nitrites two solutions will be required. 
Sulfanilic Acid solution is prepared by dissolving 1 g. 
of the acid in 100 c.c. of hot water. To prepare 
naphthylamine hydrochloride t the other reagent, boil 
a half gram of the salt in 100 c.c. of water for 10 
minutes. 

To make the test place 50 c.c. of the water in a 
tall test tube and add 1 c.c. of concentrated hydro¬ 
chloric acid, that is, the strongest acid. Follow this 
with 2 c.c. each of sulfanilic acid and naphthylamine 
hydrochloride. Cover the test tube with a glass plate 
and allow it to stand for 30 minutes. If nitrites are 
present, a pink color will appear. By the intensity of 
the color you may estimate the amount of nitrite. 
Wholesome water seldom contains even the faintest 
trace. 

To test for nitrates get your druggist to prepare 
for you a solution of phenol-sulfonic acid. Evaporate 
100 c.c. of water to dryness in a porcelain dish over 
steam and add to it 2 c.c. of the above reagent. Whole¬ 
some water will give no red color within 10 minutes. 


106 The Boys' Own Book of Science 

At the end of that time add a few c.c. of ammonia 
water. If nitrates are present, a yellow color will 
appear. Since sodium nitrate is a common fertilizer, 
nitrates are more apt to be present than nitrites, but 
in no case should there be more than a trace. 

You may also test for nitrates by adding to 50 c.c. 
of the water 2 c.c. of concentrated sulfuric acid and 
a minute quantity of a compound known as brucin . A 
red coloration proves their presence. 

Sometimes water contains lead dissolved from the 
pipes through which it has passed. To test for it 
evaporate 100 c.c. of the water to one-tenth that vol¬ 
ume and add a few drops of potassium chromatic solu¬ 
tion. If lead is present, a yellow precipitate will form. 

Good drinking water will never contain more than 
traces of phosphates. Again get your druggist to pre¬ 
pare for you a solution of ammonium molybdate. Then 
evaporate 100 c.c. of the water to dryness and moisten 
the residue with a few drops of the reagent. Warm 
gently and look for a yellow color. If it appears, 
phosphates are present, and this would indicate animal 
contamination. 

Another method of testing for organic matter is 
by the oxidizing action of potassium permanganate. 
Prepare a solution of this salt by dissolving 0.2 g. in 
a half liter of water (500 c.c.). Also very slowly 
pour 20 c.c. of concentrated sulfuric acid into 175 c.c. 
of distilled water and allow the mixture to cool. 

Into a clean porcelain evaporating dish measure 100 
c.c. of the water and add 10 c.c. of the acid. Heat the 












Testing for organic matter in water. 


107 











The Examination of Water 109 

contents of the dish nearly to boiling and add from 
your burette, drop by drop, the solution of potassium 
permanganate, stirring and heating after each addi¬ 
tion. Continue this process until a permanent tinge 
of pink appears. If organic matter is present, it will 
take oxygen from the potassium permanganate and 
decolorize it. If more than 4 or 5 c.c. of the per¬ 
manganate are decolorized by 100 c.c. of water, there 
is probably some source of pollution. 

These water tests are giving you a great deal of 
practical laboratory work, and I am sure that you 
are enjoying them. There is never anything much 
more fascinating than doing real analytical work. 

Mineral Analysis of Water.—Although to know 
whether water is pure and fit to drink is the most vital 
question concerning it, still for industrial purposes 
the mineral compounds present must be known. Prob¬ 
ably the most important item that comes under this 
head is that of hardness. You know that some water 
feels harsh to the touch and roughens and chaps the 
skin. Other water like rain water feels soft and has 
just the opposite effect upon the skin. These were 
the original meanings of the terms “hard’' and “soft” 
as applied to water. But the action of water with 
soap is now taken as an indication of its hardness. 

To test for the degree of hardness obtain a good 
quality of liquid soap as free from color as possible. 
Place some of this in a test tube fitted with a cork 
in the opposite sides of which you have cut two small 
notches. This will serve as a dropping bottle. 


I IO 


The Boys’ Own Book of Science 

Distilled water is perfectly soft. To two-thirds 
of a test tube of this water add one or two drops of 
soap. Observe that the soap produces no cloudiness 
in the water. That is the first indication that water 
is soft. Next place your thumb over the mouth of 
the test tube and shake it thoroughly. Copious suds 
at once form and do not disappear for several hours. 

Now add a few drops of a solution of calcium 
chloride to a half test tube of water and follow it 
with soap. Note that cloudiness appears in the water 
and a precipitate forms. Shake the tube. Froth and 
bubbles may form, but not suds. This is typically hard 
water. Natural water is not usually as hard as this 
prepared sample but the action is the same. The pre¬ 
cipitate that forms is the cause of the scum which ap¬ 
pears on the sides of a wash bowl or bath tub. In the 
laundry it is difficult to wash this substance from the 
clothes and it behaves just as so much dirt. In fact 
dirt is defined as matter out of place. 

Prepare another sample of hard water by dissolving 
a pinch of magnesium sulfate, ordinary Epsom salt, 
in half a test tube of water. Test this with soap. You 
will observe that a precipitate forms again and that 
no suds appear on shaking. Calcium and magnesium 
compounds are the causes of hard water in nature. 
But there are two kinds of hardness —temporary and 
permanent . One may be removed by boiling while the 
other requires chemical treatment. 

Temporary hard water in nature is produced by the 
solvent action of water containing carbon dioxide in 


111 


The Examination of Water 

passing over limestone rocks. It is this action that 
hollows out limestone caverns and builds stalactites 
and stalagmites. You may prepare temporary hard 
water by passing carbon dioxide through limewater 
until the precipitate which first forms dissolves and 
the water becomes clear. 



Figure 15. 

Preparation of temporarily hard water by passing carbon dioxide through 

limewater. 

Set up your gas generator as you did in the chapter 
on the atmosphere and with marble chips and hydro¬ 
chloric acid prepare the gas. Pass the delivery tube 
to the bottom of a test tube nearly full of limewater 
and bubble the gas through it until the white precipi¬ 
tate that first forms entirely dissolves (Fig. 15). 
Divide this solution into two portions. Dilute one 
with a little water and add soap. You find it hard 
of course. Heat the other portion in the flame. The 


















I 12 


The Boys' Own Book of Science 

white precipitate that dissolved in an excess of carbon 
dioxide will reappear. When this happens, filter off 
the precipitate, dilute the filtrate with a little distilled 
water, and add soap. This time you will find the 
water soft. Temporary hard water is one of the chief 
causes of the “boiler scale” that forms on the inside 
of tea kettles, steam boilers, and hot water pipes. 
Place some of the scale from the inside of a tea kettle 
in a test tube and add hydrochloride acid. You will 
obtain a vigorous effervescence of gas, which you may 
test with limewater for carbon dioxide. 

Prepare another sample of the temporary hard 
water and add to it limewater. You will observe the 
formation of a white precipitate. This is another 
method employed to soften such water for industrial 
use. 

Permanent hardness is due to the presence in water 
of calcium and magnesium chlorides and sulfates. 
Shake a little Plaster of Paris (calcium sulfate) with a 
test tube of water, filter, and divide the filtrate into 
two parts. To one portion add a fairly strong solu¬ 
tion of ordinary washing soda, or sodium carbonate. 
A white precipitate will form. Filter this off and test 
the filtrate with soap. Copious suds will form and 
you will find that the water has become quite soft. 
This is the most common method of softening per¬ 
manently hard water. In the same way the hardness 
may be removed from water containing magnesium 
sulfate. 

Boil the other portion of the above filtrate and note 


The Examination of Water 113 

that a white precipitate forms. This is because calcium 
sulfate is less soluble in hot water than in cold. This 
is one of the causes of boiler scale. Filter off the 
precipitate and test the filtrate for hardness. You 
will find it still hard. And, because such hardness 
cannot be removed by boiling, it is called perma¬ 
nent. 

A large scale method of removing hardness has 
recently come into very wide use in laundries, textile 
mills, and wherever industries require soft water in 
large quantities. It consists in passing water through 
immense filters containing an artificially prepared 
mineral substance, known under a variety of trade 
names such as “permutit,” “softite,” “refinite,” etc. 
The water issues from these filters perfectly soft. 
After a certain period of use, the filter must be re¬ 
generated, but this is easily done by allowing a strong 
solution of brine to stand in it overnight. Upon 
drawing off the brine and washing out the filter, it is 
good for another period of service. 

Now to test the sample of water which you have 
for hardness add to 25 c.c. of it soap, a drop at a time, 
shaking the test tube after each addition, and count 
the number of drops required to give permanent suds, 
that is, a small depth of suds which do not disappear 
immediately after shaking. To estimate the degree 
of hardness compare the amount of soap used with the 
water being tested and with that required for an equal 
volume of distilled water. 

To determine whether the hardness is temporary or 


114 The Boys’ Own Book of Science 

permanent boil 25 c.c. of the water and test with soap. 
If no more soap is now required than with the same 
volume of distilled water, the hardness is all tem¬ 
porary. If the boiling seems to make no difference in 
the amount of soap required, the hardness is all per¬ 
manent. If the amount of soap required is less than 
it was before boiling but more than with the same 
volume of distilled water, the hardness is of both 
kinds. 

You should learn to test for a number of the 
important mineral constituents of water. These are 
usually present in quite small quantities and, in order 
to obtain good tests, it will be necessary to evaporate 
a quart of water to the volume of about a half a pint. 
This may be done in a granite basin over the kitchen 
stove. If a precipitate forms, filter it, catchng the 
filtrate in a clean beaker. Replace the beaker with a 
test tube and pass through the filter paper a little 
hydrochloric acid. If in doing this effervescence oc¬ 
curs, carbonates are present. 

To a portion of the main filtrate add a few drops 
of a solution of barium chloride. If a precipitate 
forms which will not dissolve in dilute hydrochloric 
acid, sulfates are present in the water. 

If another portion gives with silver nitrate a white 
precipitate, which is insoluble in dilute nitrate acid, 
chlorides are present. 

Iron may be tested for by adding to a little of the 
filtrate a few drops of potassium sulfocyanate solu¬ 
tion or potassium ferrocyanide solution. A red color 


The Examination of Water 115 

in the one case or a blue color in the other shows the 
presence of iron. 

Calcium salts may be tested for with a solution of 
ammonium oxalate. Add a few drops of the reagent 
to a little of the filtrate and note whether a white pre¬ 
cipitate forms. If so, calcium is present. 

The test for lead has already been given. 

We have now given water a very thorough examina¬ 
tion and you have gained by it a considerable knowl¬ 
edge of chemistry and excellent drill in laboratory 
work. But we have only begun to experiment. Some 
of the most interesting work lies ahead. 


Chapter 12 


SIR HUMPHRY DAVY 

I F you should suddenly find yourself the master in 
the best equipped laboratory in the land sur¬ 
rounded with all the conveniences that money and 
science could provide, fortunate, indeed, would you 
consider yourself. But such was the happy fate that 
befell Sir Humphry Davy, when he was not Sir 
Humphry, but just plain Humphry Davy. In many 
respects young Davy lived in a most favored time for 
amateur scientists. All scientists were more or less 
amateurs in those days, and it did not require a college 
training and a number of degrees to obtain real posi¬ 
tions in the scientific world. 

Davy was born in Penzance, Cornwall, England, in 
1778, the son of a woodcarver. One of his early 
pastimes was to experiment in a home laboratory in 
the loft of the house. And more than once his chemical 
mishaps aroused the opposition of his elders, who 
feared that he would some day blow them all into 
the air. But experiment, Davy would, for he was a 
born scientist. Yet Davy was a genuine boy. He loved 
to fish and he did not do very well in school. At the 
death of his father, Davy was apprenticed to a neigh¬ 
boring physician and assisted him in the preparation 

116 


Sir Humphry Davy 117 

of his medicines. This was just what the young scien¬ 
tist wanted, for now he had a real laboratory in which 
to experiment. But the numerous explosions which 
he devised soon led his employer to let him go. 

In the meantime Davy had fortunately secured an 
introduction to Dr. Beddoes of Bristol, who was just 
establishing a “pneumatic institute” for the prepara¬ 
tion of new gases and the discovery of their physio¬ 
logical effects upon the human system. Dr. Beddoes 
was looking for a director of his institute and, learning 
of Davy’s great interest in chemistry, asked him to 
accept the place. Davy was delighted and immedi¬ 
ately took up his new duties. Imagine it, if you will, 
an untrained home-laboratory worker placed at the 
head of an important scientific institution. But he 
plunged into his new work with zest and quickly dis¬ 
covered the intoxicating and soothing effects of the 
anaesthetic called nitrous oxide, but better known as 
“laughing gas.” It is the same gas that dentists use 
today, but Davy was the first to experiment with it. 
He discovered that upon breathing it the patient first 
becomes hysterical and then unconscious. News of the 
discovery quickly spread throughout England and 
Davy found himself famous. Everyone wanted to try 
the properties of the new gas, and demonstrations with 
it became the fad of the hour. In breathing carbon 
monoxide, however, Davy became ill and nearly lost 
his life. It is a good thing that not many gases were 
known in those days or he surely would have been a 
martyr to science. 


118 The Boys Own Book of Science 

When Davy had just passed twenty-one, Count 
Rumford established the Royal Institution in London, 
and so renowned had the youthful scientist become 
that he was called to be assistant professor of chem¬ 
istry in the first important scientific laboratory ever 
founded in England. As Davy sat in the stagecoach 
which bore him from Bristol to London, he dreamed 
of future wealth and fame, and well were these dreams 
fulfilled, for he became one of the foremost scientists 
of Europe. So popular were his lectures that all 
London flocked to hear him, and for his great dis¬ 
coveries the king knighted him. And all this came to 
a mere youth who taught himself chemistry and learned 
the science of laboratory technique from his own 
instruction. 


Chapter 13 
SOAP 


A fter our study of water I think you would expect 
soap to be the next subject. Soap and water 
usually go together. Soap-making is one of the oldest 
chemical processes known. Does your mother ever 
make soap at home? Our grandmothers did. I re¬ 
member the old ash-leach into which we put all the 
wood ashes from the fires, and through which each day 
we poured a pail of water. The water leached down 
through and produced lye f which we caught in an iron 
kettle. This lye was a yellowish liquid and exceedingly 
caustic. Then every few weeks we placed all of the 
scraps of fat that had accumulated about the house¬ 
hold into another huge iron kettle, called a caldron 
kettle, and raised about a foot off the ground by large 
stone blockings. Over these fats we poured the lye 
mixed with water. Next we built a fire and heated the 
contents of the kettle for several hours, stirring the 
mixture frequently with a wooden paddle. During 
this process the lye united with the fat to form soap. 
The name given to this soap-making process is 
saponification. When all the fat had been saponified 
the soap would slip freely from the wooden paddle and 
the process was at an end. This soap was always soft 


120 


The Boys’ Own Book of Science 

and was kept in earthen jars. It was the only soap 
used in the early days, but it was very harsh on the 
skin and injurious to fabrics, especially woolens. 

The preparation of soap even today employs the 
same method. We will start you off with a simple 
laboratory process and follow it with one on a larger 
scale. Pour into a 500 c.c. flask 50 c.c. of cottonseed 
oil and 15 c.c. of a solution of sodium hydroxide having 
40 g. of the solid hydroxide to 100 c.c. of water. F’it 
into the neck of the flask a one-hole rubber stopper 
carrying a 2-foot length of glass tubing. Place the 
flask on your ring-stand and heat the mixture gently 
with a small flame for at least two hours. If 100 c.c. 
of alcohol have been added to the mixture the time 
of heating may be cut in half. Unless the alcohol is 
used, the stopper and glass tubing will not be required. 
At the end of this time pour the mixture into an 
enameled pan and boil it with constant stirring until 
all the alcohol has been driven off or until it becomes 
a pasty mass. Then let it cool. 

Test a little of the product with soft water and note 
whether it produces suds freely. Wash your hands 
with it. 

To prepare soap on a larger scale obtain from the 
grocery store a small can of concentrated lye and a 
pound can of Crisco. Place a half pint of cold water 
in a large beaker and dissolve in it 4 big tablespoon¬ 
fuls of the lye, being careful not to get any of it on 
your skin or clothes. Put the Crisco into a 2-quart 
enameled pan or kettle and heat the fat until it melts 



Making soap. 


121 









123 


Soap 

and becomes lukewarm. I hen pour the solution of 
lye into the melted fat very slowly and with constant 
stirring. Continue the stirring until you obtain a 
thick, pasty mass. Pour the product into a shallow 
oblong basin and let it stand for a week. Cut the soap 
into small cakes and distribute them to your friends 
as evidence that you have become a manufacturing 
chemist. 

\ ou will find it very interesting to prepare special 
soaps. While the soap is still thin stir into it some 
dyestuff and you will have a colored soap. A dash of 
nitrobenzene or toilet water will give a perfumed soap. 
A 5 per cent solution of carbolic acid stirred into the 
batch gives a medicated soap. Mentholatum or 
camphor may be substituted for the carbolic acid. 
Fine sand gives scouring soap. Oatmeal or cornmeal 
will give a U beauty soap.” 

Soft soap is made by saponifying a fat with potas¬ 
sium hydroxide instead of sodium hydroxide. Pro¬ 
ceed exactly as you did with the first soap made above, 
but in place of the 15 c.c. of sodium hydroxide use 21 
c.c. of a solution of its twin brother, potassium hydrox¬ 
ide, containing 40 g. to 100 c.c. of water. After the 
boiling is complete, pour into the soap 200 c.c. of water 
and mix thoroughly. Put this up in small bottles and 
distribute it to your friends. 

Good toilet soap should contain no free alkali. To 
a freshly cut piece of toilet soap add a few drops of an 
alcohol solution of the indicator phenolphthalein. If 
free alkali is present a pink color will appear. Free 


124 The Boys Own Book of Science 

alkali is harsh on the skin and in laundry soaps injures 
woolens and delicate fabrics. 

Hard Water Wastes Soap.—To determine some¬ 
thing about how great this waste is place ioo c.c. of 
distilled water in a glass-stoppered bottle and add to 
it from a burette liquid soap a drop at a time followed 
by shaking until a suds that will remain permanent for 
5 minutes is obtained. From the readings of the 
burette note the amount of soap used. Then repeat 
the test using tap or well water. The difference in 
the amounts of soap used in the two cases will enable 
you to estimate the waste resulting from the use of 
hard water. Of course this will vary with the water 
used. 

The cleansing action of soap was for a long time 
more or less of a mystery. We think we now know 
about this. To understand the action of soap with 
grease we must know what an emulsion is. Place 2 or 
3 drops of olive oil in half a test tube of water and 
shake the mixture. Set the test tube aside. In a few 
moments you will observe that the oil rises to the sur¬ 
face of the water. The two will not stay mixed. Now 
add to the test tube a few drops of liquid soap and 
shake again. This time you obtain a permanent mix¬ 
ture. The oil will not rise to the surface even upon 
standing for a long time. You have emulsified the 
oil, and that is exactly what soap does with grease on 
your hands or on goods that are being washed. The 
soap emulsifies the grease and causes it to slip off. 

Just plain dirt actually adheres, or sticks to soap, 



Soap 125 

which wraps itself about the dirt in a tiny film 
and carries it away. 

Another factor in the cleansing action of soap is its 
alkaline reaction. Dissolve a little soap in water and 
test it with phenolphthalein indicator. A pink color 
will always result showing the presence of an alkali, 
or a base. This is formed by the reaction of the soap 
and water with each other. Since an alkali will attack 
grease and dirt, it also assists in the cleansing action. 

I think you will find the examination of a soap 
powder interesting. Washing powders usually con¬ 
tain ground up soap, sodium carbonate or borax, and 
often some gritty substance such as fine sand or pumice 
stone. Weigh out about 10 g. of the powder. Trans¬ 
fer it to a beaker and cover it with 200 c.c. of hot 
water. Stir this thoroughly to dissolve all the soluble 
matter. Then filter and wash the insoluble matter on 
the filter with hot water a number of times, passing 
the water through the filter. Examine this residue. 
If you wish to determine the per cent, dry the filter 
on a watch glass placed over a water bath and weigh 
the residue. The difference between this weighing and 
the original weight of powder taken will be the amount 
of insoluble matter plus the weight of the filter paper. 
To obtain an accurate result it will be necessary to 
weigh a filter paper and subtract it from the apparent 
residue. 

To test for the carbonate place a little of the pow¬ 
der in a test tube and add hydrochloric acid. If 
effervescence occurs, incline the test tube so that the 


126 The Boys’ Own Book of Science 

mouth is slightly above the horizontal and let the gas 
slide into another test tube containing about 2 c.c. of 
lime-water, but do not let any of the liquid pass into 
the limewater. Shake the test tube containing the lime- 
water and note that a white precipitate forms, showing 
the presence of carbon dioxide and consequently of a 
carbonate. 

To test for borax dissolve a little of the powder in 
hot water, filter the solution, and add to the filtrate 
hydrochloric acid. Dip a piece of tumeric paper into 
this solution and dry it by holding the paper high over 
the flame. If borax is present, you will note that the 
paper has a tinge of red which turns black upon the 
addition of ammonia water, but that dilute hydro¬ 
chloric acid will restore the color. 

To learn the action of borax in soap dissolve a little 
borax in a test tube of water and try the action of the 
solution on red litmus paper. The blue color that ap¬ 
pears shows that borax gives an alkaline reaction and 
is therefore a cleanser. In addition borax softens 
water. Prepare a sample of hard water by shaking a 
little Plaster of Paris or Epsom Salt with a test tube 
of water and filtering. Add to the filtrate a little pow¬ 
dered borax, shake well, heat nearly to boiling and 
filter again. Test the filtrate with soap. Do you find 
that it has been softened? 

In the manufacture of soap a very valuable by¬ 
product is obtained. It is glycerin so much used in 
the making of explosives. In the soap which we have 
made the glycerin remains in the soap. 


Chapter 14 

EXAMINATION OF TEXTILE FIBERS 


W HEN you buy a suit and the salesman tells you 
that it is all wool, you want to be sure that he 
is telling you the truth. You do not want it to be half 
cotton. But how are you going to know. You will 
have to turn chemist. From early times fabrics have 
been woven from four principal kinds of fibers—wool, 
cotton, silk, and linen. Two of these are of animal 
origin and two of vegetable. In addition we now 
have artificial silk. 

The burning tests are the easiest to apply, so we 
will take them first. Obtain samples of each of the 
four chief kinds of fabrics and ravel out some of the 
threads. Ignite with a match each kind in succession 
and note in each case the character of the flame, the 
odor, and the ash. I think you will find that the 
cotton burns up quickly, giving a bright yellow flame 
and little odor, and leaving a fine white ash. If much 
of the cotton is burned you will probably detect the 
odor of burning wood. Cotton and wood are similar in 
composition. Linen fibers behave in the same way. 
But you will find that the wool fibers do not burn so 
readily. They give a flickering flame with a disagree¬ 
able odor like that of burnt hair, and leave a hard 

127 



128 The Boys Own Book of Science 

black residue of unburned carbon. These properties 
are characteristic of animal fibers when burned. Now 
try the silk. You will see that it resembles wool, but 
it burns more quickly, the flame is blue, and the odor 
is not as noticeable. But there is still an unburned 
residue. Try the burning test on artificial silk. Which 
one of the above fibers does it resemble? How could 




Figure 16. 




Microscopic appearance of wool, cotton, silk, and linen fibers, named in order. 


you distinguish real silk from artificial silk? I think 
you will find this easy to answer. How does mercer¬ 
ized cotton behave when burned? Would you have 
any difficulty in distinguishing it from either kind of 
silk? 

A microscopic examination of fibers is often made. 
Possibly you will be able to detect some differences 
with a small hand magnifier, but, if by any chance 
you can get the use of a compound microscope, 
















129 


Examination of Textile Fibers 

do so. If you are a high school student, this can 
be easily arranged. Wool fibers seem to be made 
up of a succession of small segments, which overlap 
each other like the scales of a fish or shingles 
on a roof. A cotton fiber has the appearance of two 
twisted strands. Silk fibers seem to be long, narrow, 
cylindrical threads. Linen fibers are similar to silk 
but they are wider, not so straight, and often have 
cross lines. 

Now for the chemical tests. The alkali test is best 
for distinguishing cotton and wool. From the grocery 
store obtain a small can of concentrated lye. Into a 
small agate basin placed over your Bunsen burner put 
4 big tablespoonfuls of the lye. Add a pint of water 
and bring it to a boil. Then drop into this solution a 
square of some fabric, which you think is wool or 
partly wool and partly cotton. Boil it slowly for a few 
minutes. If the sample completely dissolves, it is all 
wool. If it does not, the insoluble residue is probably 
cotton. In case of any such residue, remove it with 
a glass rod and wash out the fibers thoroughly in 
several changes of cold water. Then dry them, and 
apply the burning test. Very often so-called “all 
wool” contains considerable cotton. 

To distinguish wool and silk drop threads of each 
into small beakers containing concentrated hydro¬ 
chloric acid. After a few minutes you will find that 
the silk has completely dissolved, but that the wool has 
been little affected. They are both soluble in lye. Of 
course you understand that, chemically, lye is sodium 


130 The Boys’ Own Book of Science 

hydroxide, and that either this or potassium hydroxide 
may be substituted for it. 

To distinguish real silk from artificial silk or mer¬ 
cerized cotton place three small beakers upon the 
table, each containing concentrated hydrochloric acid. 
In the first put real silk, in the second artificial silk, 
and in the third mercerized cotton. Boil each for two 
or three minutes. Which dissolves? The burning 
test may also be used. 

To distinguish cotton and linen is more difficult. 
There is no good chemical test. The best means is 
the microscope, the differences in the appearance of 
the fibers having already been described. Another 
test consists in boiling small pieces of the goods in 
olive oil for about five minutes. Upon examining them 
against a dark background, the linen looks dark, while 
the cotton appears light. 

To determine the percentage of cotton in mixed 
goods cut a piece of the cloth about 3 inches square 
and dry it for several minutes in your evaporating dish 
placed high over a small flame. If you have a ther¬ 
mometer, keep the temperature at about 100 degrees 
Centigrade. Then allow the cloth to cool without 
removing from the dish. Transfer it to your balance 
and weigh it as accurately as possible with the set of 
weights which you have. Place it in a beaker and boil 
it with a solution of either sodium or potassium 
hydroxide containing 20 g. of the alkali to 100 c.c. of 
water. Continue the boiling for three minutes. Pour 
off the alkali and wash the residue thoroughly with 





Determining the percentage of wool in a fabric. 


r 3i 


■ 










Examination of Textile Fibers 133 

water. Put a drop of phenolphthalein indicator in the 
beaker and add dilute hydrochloric acid until the pink 
color disappears. This will neutralize the alkali left 
in the shreds. Wash thoroughly with water and dry 
as above at about ioo° C. Cool and weigh again. 
Divide the loss of weight by the weight of the original 
piece of goods and you will have the percentage of 
wool. 

The effect of strongly alkaline laundry prepara¬ 
tions on woolen goods may be determined by im¬ 
mersing a piece of flannel in a hot solution of ordinary 
washing soda. Use a tablespoonful of the soda to a 
pint of water. Keep the solution nearly at the boiling 
temperature for half an hour. Then take the fabric 
out, rinse thoroughly, and examine to see what has hap¬ 
pened to the goods. Washing soda is strongly alka¬ 
line and so are many laundry soaps and powders. It is 
used to soften water, but borax gives only a mildly 
alkaline reaction and for that reason is better. 

To learn for yourself the difference between wash¬ 
ing soda and borax in their effects on woolens, repeat 
the above test substituting the latter. 


Chapter 15 

MICHAEL FARADAY 

S urely you must have heard of Michael Faraday, 
the poor apprentice lad who sought to become 
assistant to the renowned Sir Humphry Davy. One 
day a generous friend gave Faraday a ticket to a 
course of lectures being given by Davy at the Royal 
Institution. The eloquence of Davy’s delivery and 
the skill in demonstration, for which he was so justly 
renowned, aroused the enthusiasm of the young ap¬ 
prentice. Thenceforth he felt that business would 
forever be distasteful to him and that nothing would 
satisfy his heart’s desire but the life of a scientist. 
Faraday had taken full notes of the lectures and made 
drawings of the apparatus used in demonstration. 
These he sent to the great Sir Humphry with a care¬ 
fully written note telling of his ardent desire and re¬ 
questing an appointment as laboratory assistant. Davy 
endeavored to discourage the young enthusiast from 
such a life but without avail, and then promised to give 
him a place at the first opportunity. Imagine Faraday’s 
joy when a few weeks later a coach drew up at his 
humble lodgings and a liveried footman bore him a 
note announcing his appointment to the much coveted 
position. 


134 


Michael Faraday 135 

And again we have an untutored young man, with¬ 
out previous experience, coming into a laboratory posi¬ 
tion of great responsibility and wonderful opportunity. 
Faraday’s duties were to set up apparatus for Davy’s 
lectures, assist him in performing the demonstrations, 
and still better to assist in making the discoveries 
which formed the basis of the lectures. Can you 
imagine a more fascinating beginning for the would-be 
scientist? Here he was, as if by magic, established in 
the best equipped laboratory of England and acting as 
assistant to the foremost scientist of Europe. 

But Faraday improved his opportunities. He 
worked incessantly. He studied to obtain an educa¬ 
tion at night, and he experimented in every spare 
moment during the day. He went with Davy on a 
trip to the continent and there met the leading scien¬ 
tists of other lands. In a few years he was lecturing 
himself and developing that power of presentation 
which was to make him the most popular lecturer of 
his time. When Davy resigned as Director of the 
Royal Institution, Faraday became his successor and 
for more than forty years was known as one of the 
most distinguished scientists of any country. In those 
years he made some of the most notable discoveries 
of the last century. In electricity he laid the founda¬ 
tion for the marvelous developments of the present 
age. 

And this life of wonderful achievement came from 
a boy’s desire to experiment and become a scientist. 


Chapter i6 


STAINS AND BLEACHES 

T HE subject of stains and bleaches opens up for us 
a whole new realm of chemical investigation. 
Scarcely a week goes by that some boy does not come 
to my laboratory to have an ink stain or a grease spot 
removed. Very often a boy comes with gum on his 
trousers. One of his particular friends has contrived 
to have him sit on a wad of this apparently modern 
necessity. At such times a little knowledge of applied 
chemistry is very valuable. 

Suppose we start with stains. A stain may be either 
physical or chemical. By physical I mean that no 
chemical change has taken place between the fabric 
and the substance causing the stain. Such stains are 
most easily removed. It is frequently impossible to 
remove a chemical stain. 

For the removal of a large number of stains two 
solutions will be required. They are: 

i. Tartaric or oxalic acids—50 g. to 250 c.c. of 
water. 

2. Twelve and one half grams of ordinary chloride 
of lime to 250 c.c. of water. Boil this until a 

pink color appears, then filter and add 125 c.c. of 

136 


Stains and Bleaches 


137 


cold water. (Chloride of lime may be had at a 
grocery store, but be sure that it comes in a sealed 
metal can). 

Keep these solutions in stoppered bottles. The 
first will keep indefinitely, but the second must be re¬ 
newed at frequent intervals. 

Ink stains are easily removed with these two solu¬ 
tions, especially if they are fresh. Try them both on 
fresh and old specimens of writing. Wet the ink with 
No. 1, take up the surplus liquid with a blotter, and 
then apply solution No. 2. Usually the ink will dis¬ 
appear. Ammonia will often remove fresh ink stains. 

Try these solutions on fruit, tea, or coffee stains. 
After applying both solutions, rinse the material with 
water and, if necessary, apply them again. After the 
color has been removed, a yellow spot will often re¬ 
main. In such a case, which occurs most often with 
woolen goods, apply hydrogen peroxide. This will 
oxidize the coloring matter and remove it. 

Grease spots are probably the most common and 
troublesome stains. To remove them apply liberal 
quantities of gasoline, carbon tetrachloride, or ben¬ 
zene. Follow this treatment with soap suds and am¬ 
monia. If a grease spot is fresh, French chalk will 
usually absorb it. If not, use any one of the above 
solvents and then apply the chalk. (Carbon tetra¬ 
chloride is “Pyrene,” so much used in fire extinguishers. 
It is one of the best solvents known.) 

Stains from dyes may usually be removed by appli- 


138 The Boys Own Book of Science 

cations of solutions No. 1 and No. 2. Chloroform 
is also an excellent solvent for these stains. So is 
carbon tetrachloride. 

Gum may be removed by rubbing with carbon tetra¬ 
chloride or chloroform. They loosen the sticky stuff 
and enable you to rub it off. Both evaporate very 
rapidly and leave no stain themselves. 

Iodine stains are often very annoying to a labo¬ 
ratory worker, but they are easily removed. Am¬ 
monia water will usually dissolve them. A dilute solu¬ 
tion of washing soda also does. If you have potassium 
iodide a ten per cent solution of it, that is, 10 g. to 100 
c.c. of water, will do the trick. Denatured alcohol 
also dissolves iodine. 

Spots of iron rust frequently occur on white goods. 
But, since iron rust consists of iron oxide which is 
soluble in dilute acids, the problem is easily solved. 
Your grandmothers covered the spot with lemon juice 
and salt and exposed it to the sun. The lemon juice 
contains citric acid, which dissolves the rust, while the 
salt serves to hold the liquid and keep the goods moist. 
A warm saturated solution of oxalic acid applied with 
a soft sponge will also remove these spots. But re¬ 
member that this acid is poison. 

Acid stains are the most annoying to a home-labo¬ 
ratory worker. About the only thing to do is to 
neutralize such stains with ammonia, and this should be 
applied just as soon after the acid falls upon the 
clothing as possible. If the acid has had time to do 
its work very little can be done. In the course of 


Stains and Bleaches 


139 


many years of laboratory work I have ruined more 
suits of clothes than I like to remember. You will find 
that your best protection consists in wearing a labora¬ 
tory coat similar to an automobile duster. 

In case of paint either carbon tetrachloride or benzol 
will remove the spots. Turpentine followed with soap 
and ammonia is also good. Similar treatment may be 
used with varnish } but equal parts of wood alcohol, 
benzol, and acetone are better. 

Mildew, and ink spots on rugs, may frequently be 
removed by an application of a solution of tartaric 
acid followed by “Javelle” water. The directions for 
preparing Javelle water will be found on the cans of 
chloride of lime which may be had from a grocery 
store. 

BLEACHING 

The bleaching of fabrics has become a very impor¬ 
tant branch of the textile industry. It is also often 
desirable to bleach goods in the household. But in 
order to remove a color you must produce a chemical 
change. The dye must be changed into a colorless 
substance. Furthermore this must be done without 
injury to the fabric. Sunlight is a great bleaching 
agent. You know that curtains and other colored 
goods often fade under the influence of the sun’s rays. 
That is because the sunlight is able to produce chemical 
effects. 

Bleaching Cotton.—The best bleaching agent for 
cotton is chlorine, but we seldom use chlorine gas 


14° The Boys Own Book of Science 

directly. The chlorine is absorbed in slaked lime and 
converted into bleaching powder, better known as 
ordinary chloride of lime. Obtain a can of this from 
the store and make a paste by stirring 2 g. of the 
powder into 100 c.c. of water. (Remember that un¬ 
less bleaching powder comes in a sealed metal con¬ 
tainer, it is worthless). 

Then prepare a very dilute solution of hydrochloric 
acid, about 1 c.c. of the concentrated acid to 25 c.c. 
of water. Also have at hand a solution of photog¬ 
rapher’s hypo containing 5 g. of the salt to 100 c.c. 
of water. Now cut some strips of colored calico and 
dip them into the paste of bleaching powder. After 
a moment or two place them in a small beaker contain¬ 
ing the dilute hydrochloric acid. Continue this pro¬ 
cess, alternately dipping the calico into bleaching pow¬ 
der and acid until the color is removed. Finally wash 
the fabric thoroughly with water and dip it into the 
solution of hypo. 

There is considerable chemistry involved in this pro¬ 
cess. The hydrochloric acid acts upon the bleaching 
powder to liberate chlorine. The chlorine then acts 
upon the water present and liberates oxygen. It is 
really the oxygen that does the bleaching. The hypo 
absorbs any excess of chlorine left upon the goods, 
for unless this is done the chlorine will weaken the 
fiber of the cloth. 

Cotton goods may also be bleached directly by 
chlorine, but, since the preparation of this poisonous 



Bleaching cotton fabric with chloride of lime. 


141 










Stains arid Bleaches 


143 

gas in a small laboratory is somewhat dangerous, we 
had better not attempt it. 

To bleach cotton on a larger scale stir thoroughly 
for some time the contents of a can of chloride of lime 
with 1 gallon of water and allow the mixture to settle. 
Pour off the clear liquid. Prepare equal volumes of 
the solutions of hydrochloric acid and hypo, using the 
same proportions as before. Also prepare a dilute 
solution of ordinary washing soda. Rinse the goods in 
the acid. Then pass them slowly through the solution 
of chloride of lime. Follow this treatment by dipping 
the goods first in the solution of washing soda and 
then in the hypo. Rinse thoroughly in water. If the 
color has not been entirely removed, put them through 
the process again. In some cases it may be necessary 
to leave the material in the chloride of lime for a 
short time. If a yellow color remains destroy it with 
hydrogen peroxide. 

Bleaching Wool.—Since chlorine injures animal 
fibers, some other chemical agent must be employed. 
The substance that works best is our old friend sul¬ 
fur dioxide. This gas, as you have doubtless dis¬ 
covered, has a strong odor, and it is also an important 
disinfectant. 

Place two or three teaspoonfuls of sodium sulfite 
in a bottle provided with a stopper, to the under side 
of which you have pasted one end of a strip of colored 
flannel. Cover the sulfite with 30 c.c. of dilute hydro¬ 
chloric acid (about 1 c.c. of the strongest acid to 10 
c.c. of water). Then quickly insert the stopper so 


144 The Boys Own Book of Science 

that the strip of flannel will hang down in the bottle. 
Let the bottle stand for 24 hours. Then remove the 
cloth. You will find that the color has been bleached. 
The sulfite and acid liberate sulfur dioxide which in 
chemical language reduces the dye to a colorless 
compound. 

Straw goods may also be bleached in this same way. 
In bleaching wool and straw, hydrogen peroxide may 
be substituted for sulfur dioxide. 

Prepare a bottle of sulfur dioxide by the same 
method which you used in the chapter on Chemical 
Magic when you converted wine into water. Place in 
the gas a pink flower, a rose or carnation. In a few 
moments it will be bleached white. 

To bleach indigo bubble sulfur dioxide from your 
generator through a little water for several minutes. 
Add to this solution a small quantity of zinc dust. Let 
the mixture stand for a time. Then add some of the 
liquid to a solution of indigo. It will be instantly 
bleached. If vou have no indigo, substitute litmus 
solution. 

A Dye that will not Bleach.—Not all dyes will 
bleach. Mineral dyes belong to this class. Prepare 
a solution of potassium chromate or dichromate. Im¬ 
merse in the solution a strip of white cotton cloth. It 
is dyed yellow. But if placed in water, the color may 
be entirely washed out. It is not fast. Now prepare 
a solution of a lead salt. Either the nitrate or the 
acetate may be used. Dip the cloth first into this 
solution and then into the dye. Try to wash the color 


Stains and Bleaches 


145 


out. You cannot. It is fast. The lead salt is what 
we call a mordant. It has united chemically with the 
dye to form an insoluble color. Mordants are very 
extensively used in dyeing, particularly in the dyeing 
of cotton goods. 

Try the bleaching action of bleaching powder, sul¬ 
fur dioxide, and hydrogen peroxide upon this color. 
This is the old and familiar household dye known as 
chrome yellow and is unaffected by ordinary bleaching 
reagents. Try separately strong ammonia water, 
sodium hydroxide, and hydrochloric acid on the color: 
What happens? 


Chapter 17 

JONS JAKOB BERZELIUS 


B erzelius was a great Swedish chemist and for 
half a century was known as the “Czar of 
Chemistry.” But he taught himself most of the 
chemistry he knew. When he went to college very 
little real chemistry was known. He had to experiment 
at home, and his room was a dark dingy place with¬ 
out even a window and only an open fireplace for heat. 
One day he obtained a gas from nitric acid which he 
suspected might be oxygen. He had heard of this gas 
but had never prepared it. His supply of chemicals 
and apparatus was very limited, and he had no one 
really competent to instruct him. But he arranged 
some bottles and collected this gas over water, just 
as we do nowadays. Then into one of the bottles he 
thrust a glowing splint and to his intense joy it blazed 
up brightly and lighted his dismal room with great 
brilliancy. He knew that he had prepared oxygen 
and his enthusiasm knew no bounds. Some day you 
will make an experiment that will thrill you with the 
joy of discovery. 

Although Berzelius was to become the foremost 
chemist of Europe, his instructors in college regarded 

him as of very ordinary ability. Upon graduation the 

146 


Jons Jakob Berzelius 


147 


professor in chemistry even told him that he deserved 
to fail. But Berzelius continued his chemical investi¬ 
gations. In his simple laboratories in Stockholm he 
prepared many new compounds and increased enor¬ 
mously the world’s knowledge of chemical principles 
and processes. At length his fame spread abroad and 
chemists from other countries came to study under 
him. But they were often amazed to see the plain, 
simply furnished rooms and modest supply of ap¬ 
paratus and chemicals which sufficed for his great dis¬ 
coveries. Berzelius’ work was done during the first 
half of the nineteenth century, and in the early part 
of this period college laboratories were unknown. It 
was only through the instruction given by such ad¬ 
vanced students as this great Swedish chemist that 
chemistry progressed. 

Nothing is more delightful than such a life of dis¬ 
covery and instruction. Even in your simple labora¬ 
tory will be many conveniences and much apparatus 
which Berzelius did not have. And you, too, can make 
discoveries. They may not be new to the world, but 
they will be new to you. Some day you may make 
big discoveries, for there is still a host of them to 
be made. 


Chapter 18 


ELECTRIC FURNACES 

I F you have a i io-volt source of current, either alter¬ 
nating or direct, no other piece of your laboratory 
equipment will afford you more pleasure and service 
than an electric furnace. And you can made one your¬ 
self. Electric furnaces are of two types—the arc and 
the resistance. One derives its heating power from 
an arc giving a temperature of about 3500° C. The 
other converts electric energy into heat through the 
agency of a metal wire of very high resistance. 

We shall start with the arc furnace. The first arc 
light in history was produced by the renowned Sir 
Humphry Davy. Connecting a battery of 2000 cells 
to two pencils of carbon, he brought their ends to¬ 
gether and then, withdrawing them gradually to a dis¬ 
tance of 4 inches apart, he beheld a light of dazzling 
brilliancy and intense heat. In this arc he was 
able to melt or vaporize such substances as plati¬ 
num, quartz, sapphire, magnesia, and lime. But 
Sir Humphry’s arc light was only a curiosity. 
Dynamo current was unknown and electric cells were 
too expensive. The world had to wait for Faraday 
to discover the principle and for later scientists to 
apply it. 


148 



Electric Furnaces 


149 


Making an Arc Furnace.—The materials needed 
for this furnace are fire clay, asbestos fiber, and water 
glass. These are not difficult to obtain. You will 
probably have to send to a chemical supply house for 
the fire clay, but it is not expensive. When these sub¬ 
stances are mixed, they harden into a fireproof mass 
which is almost indestructible. 

As a form in which to shape the furnace you will 
need a small box about 8 inches long and 4 inches 
square. I used a box in which blackboard crayons 
come. In the center of each end bore a hole big 
enough to take a standard electric light carbon. Then 
in an old basin mix fire clay, asbestos fiber (short 
shreds), and water glass solution until you have ob¬ 
tained a doughy mass. Pack a layer of this about an 
inch thick as firmly as possible in the bottom of the 
box. Next set a drinking glass in the center of the 
box and thrust through the end holes two wooden pins 
the size of the light carbons which you are to use later. 
Pack around these more of the mixture as tightly as 
possible until the box is completely full (Fig. 17). 
Smooth off the top and fill in the cavities with a mix¬ 
ture of fire clay and water glass alone. In the same 
way make a cover for the furnace of the same size and 
about an inch thick. Set the box and cover in some 
warm place to dry for about a week. The top of the 
furnace is a good place. When it is dry and hard, 
break away the box, pull out the pins, and retouch the 
whole with a paste of fire clay and water glass. Strips 
of asbestos paper glued to the outside improve the ap- 


150 The Boys' Own Book of Science 

pearance. Insert light carbons to which you have at¬ 
tached copper lead wires, and your furnace is ready 
for action. 

Making a Rheostat.—But such a furnace as this 
will blow the electric fuses of your lighting circuit, un¬ 
less a suitable resistance is connected in series with it. 
A rheostat you will find necessary for much of your 


- 1 !-- 

PIN I TUMBLER PIN 

! ! 

L_J 

MIXTURE 

Figure 17. 

The arc type of electric furnace. 


electrical work, so we might as well start about making 
one first as last. A lamp-board rheostat is the cheap¬ 
est, and the easiest to make as well as one of the most 
serviceable. A dozen lamps will give you a wide range 
of current control, and should you need more current, 
additional lamps can be added. The accompanying 
figure shows the grouping for a board of 18 lamps. 
If you can find old 16 candle power carbon lamps, 


















Electric Furnaces 


I 5 i 

they will give you a larger amount of current 
(Fig. 18). 

To use this board connect your apparatus, whatever 
it may be, in series with the lamps, as indicated. Un¬ 
less you know about what current you will need, have 



all the lamps screwed loose from their sockets at the 
start. Then turn on the main switch and one of the 
branch switches. Screw in one lamp. That will give 
you a small current, something less than half an 
ampere. It will never be enough to injure any ap- 






















152 The Boys’ Own Book of Science 

paratus that you may have. Screw in another of the 
lamps on that circuit and you will nearly double the 
current. Continue to do this until all of the lamps on 
that branch have been turned on, or until you have 
obtained sufficient current for your purpose. If one 
branch does not give enough current, turn on the 
second adding one lamp at a time, as before. You 
will seldom need to use all of the 18 lamps. 

Of course you can buy a rheostat from a supply 
house, but to get a good one will probably cost you as 
much or more than the one just described. By wind¬ 
ing resistance wire, either Nichrome or German sil¬ 
ver, on a wooden core well wrapped with asbestos, 
you may make a rheostat that will be very service¬ 
able. One of Nichrome wire is the best rheostat for 
an arc furnace. A rheostat of fairly good capacity 
may be made from 210 feet of No. 26 German silver 
wire or 80 feet of No. 20 Nichrome wire. Use the 
wire bare and wind the turns as closely together 
as possible. By mounting this on a baseboard be¬ 
tween two end-pieces and providing a sliding contact 
after the fashion of a radio tuning coil, you will be 
able to obtain a variable rheostat having a wide 
range of resistance. Attach one end of the wire to a 
binding post, and make the other connection through 
the sliding contact (Fig. 19). 

Using the Furnace.—First you must learn to “strike 
an arc.” Connect the furnace in series with your rheo¬ 
stat and, if it is of the lamp-board type, turn on nearly 
all of the lamps. Then bring the ends of the carbons 


Electric Furnaces 


153 

together and quickly withdraw them about a quarter of 
an inch. An arc of dazzling brilliancy will be produced, 
so bright that for the protection of your eyes you 
should wear colored glasses. If it is too bright, turn 
off some of the lamps. To obtain more heat turn on 
more. After the arc is struck you may cut out the 
rheostat entirely. 

By means of tongs hold in the arc such metals as 
iron, copper, and aluminum. Note how readily they 



Figure 19. 

A rheostat made by winding German Silver or Nichrome wire on a wooden 
core wrapped with asbestos. One end of the resistance wires is attached to the 
center binding post. The number of turns used is regulated by the sliding 
contact. 

melt. A lump of quicklime may be heated to brilliant 
incandescence. Place just beneath the arc a small fire¬ 
clay crucible containing some pieces of sheet copper 
or copper wire. In a few minutes they will melt, and 
to melt copper requires a temperature of nearly 
1ioo° C. 

A Resistance Furnace.—Interesting as an arc fur¬ 
nace is, it is not nearly as useful as a resistance furnace. 
This type of furnace depends upon the electrical resist¬ 
ance and heat producing properties of an alloy known 
as Nichrome wire. For a long time the use of this 

















































































154 The Boys' Own Book of Science 

wire was covered by patents, and amateurs could not 
purchase it, but it is now available. 

We shall make first a crucible furnace. For this 
you will need, as before, fire clay, asbestos fiber, and 
waterglass. In addition you must have a corrugated 
Alundum core, 2^4 inches deep and 2 inches in diame¬ 
ter, some Alundum cement, and 42 feet of No. 20 



Figure 20 . 

. Alundum core for crucible type of electric furnace showing Nichrome wire 
in place. Cement must now be added. 

Nichrome wire. The first step is to wind this wire as 
closely as possible on a spindle %2 of an inch in 
diameter, leaving i foot free at each end for connec¬ 
tions. In making my furnace I got the wire wound in 
a machine shop. Stretch the coil slightly so that the 
turns will not touch and then wind it about the Alun¬ 
dum core, fitting it into the grooves (Fig. 20). By 
means of cords or rubber bands hold the turns in place, 



















Lampboard rheostat connected in series with an arc furnace. A resistance furnace 
is shown at the left. 


155 









Electric Furnaces 


157 


until you can cover the whole with Alundum cement 
to a depth of about a quarter of an inch. Put it in a 
warm place and let the cement set. 

Now obtain a box similar to the one used in making 
the arc furnace. Into the bottom press a layer of fire 
clay, asbestos fiber, and waterglass. In the center of 
this set the Alundum core and pack firmly about it 
more of the mixture until the box is level full. Bring 
the wires out to one end and secure them to binding 
posts set into the plastic mass. Cover the top with a 
layer of Alundum cement and make a cover, as you 
did for the arc furnace, but this time leave a small 
hole for a vent over the center of the pit. Then con¬ 
nect the lead wires to a 110-volt source of current and 
let the heat of the furnace itself dry it out. But re¬ 
member that you cannot obtain a high temperature 
until all the moisture has been driven out. No addi¬ 
tional resistance will be needed with this furnace, and 
you will find that, when it is dry, the crucible may be 
brought to a white heat. But first remove the box 
and smooth the outside with cement. 

Using the Crucible Furnace.—In using this furnace 
always set it upon a piece of asbestos board. To get 
up the maximum heat will require from 20 to 30 
minutes. The materials to be heated are put into a 
small crucible which is set in the fire-pit. In order to 
obtain the greatest heating power it will be necessary 
to keep the fire-pit covered. 

Making Brass.—An excellent test for your furnace 
will be the stunt of making brass, for to melt copper 



158 The Boys Own Book of Science 

requires a temperature of 1084° C. If you can do this, 
your furnace is well made. Weigh out into a small 
fire clay crucible 35 g. of copper, place the crucible in 
the pit, and bring the furnace to its highest tempera¬ 
ture. At first no doubt the copper will seem very 
stubborn. Although white hot, it will not melt. Yet 
these metals have the peculiar property of remaining 
in solid form, until a certain temperature is reached. 
Then of a sudden, when that temperature is reached, 
the metal quietly turns to liquid as simply as a piece 
of butter in a heated spoon. Presently, as you re¬ 
move the lid, you will behold a beautiful mirror of 
molten copper. 

When the copper has melted, dissolve in it 15 g. of 
zinc. After allowing a few moments for the two 
metals to mix, seize the crucible with a pair of tongs 
and plunge it into a pail of water. There will be a 
vigorous seething of the water, a dense cloud of steam, 
and then the metals will have frozen. 

You have formed an alloy. An alloy is a mixture 
of metals melted together and possessing properties 
often differing widely from those of the constituent 
metals. Alloys are tremendously important. Bronze, 
an alloy similar to brass, was known long before iron 
and steel. The early forests of Europe were felled 
with bronze axes, and bronze implements of warfare 
were used to attack the enemy and repel invasion. 
Nowadays we can make alloys to meet any require¬ 
ment of science or industry. The wire in your furnace 
is an alloy. So are solder, shot, German silver, and 


Electric Furnaces 


159 

coin metals. You may prepare other alloys in your 
furnace but many of them do not require so high a 
temperature. 

Making Quicklime. —Fill your crucible with lumps 
of marble or limestone. (To test for limestone, put 
a drop of acid upon it. If it effervesces, i.e., gives off 
a gas, it is limestone. If not, it is probably sandstone.) 
Let the marble heat at the highest temperature of the 
furnace for from one to two hours. Then let it cool. 
You have driven off carbon dioxide from the marble 
and quicklime is left. This is the same substance that 
is prepared in limekilns on an enormous scale. Quick¬ 
lime is one of the three most important raw materials 
of chemical manufacture. 

When the product of your furnace is cold, place a 
few of the lumps in a small basin and let fall upon 
them a few cubic centimeters of water. If the lime 
is well burned, it will immediately begin to get hot, 
steam will form, and the hard mass will swell and 
crumble into a powder. This process is called slaking, 
and it is what you frequently see taking place in a 
mortar box on the street. The water put on the lime 
is cold, and the heat is developed by the chemical 
action. 

A Beehive Coke Oven. —You can turn your furnace 
into a beehive coke oven. Fill the crucible with quite 
small pieces of soft coal. Bring the furnace to full 
heat, set the crucible in place, and put on the cover. 
In a few moments you will be able to light the gas 
which escapes through the vent in the cover and it will 


160 The Boys' Own Book of Science 

burn with a yellow smoky flame. In an hour you may 
allow the furnace to cool and remove the product. 
You will find that the soft coal has swollen into a light 
steel-gray substance. It is almost pure carbon, and 
coke is another of the three most important raw ma¬ 
terials of chemical manufacture. 

The Metallurgy of Copper. —Fill the crucible with 
a mixture of powdered charcoal and the wire form of 
copper oxide. You can prepare this copper oxide by 
heating a crucible full of short lengths of copper wire 
for an hour with occasional stirring. Put the mixture 
of oxide and charcoal into the furnace and heat it for 
a half hour. Then remove the crucible with tongs 
and pour its contents into a large beaker or basin of 
water. Hold the beaker under the faucet and let 
water run into it until all of the charcoal has been 
washed out. The copper is heavy and will remain 
in the beaker. If you do not have running water, 
throw water into the beaker from a pail. The char¬ 
coal has reduced the oxide to bright metal. 

Making Charcoal. —This time fill the crucible with 
small pieces of soft wood. Match sticks will serve. 
Again you will be able to light the gas that issues from 
the crucible, and the product will be charcoal. 

Another Type of Resistance Furnace. —There is 
another electric furnace called the combustion furnace, 
which some of you may be able to make. The ma¬ 
terials for this are the same as for the crucible furnace, 
except that you will use a long hollow Alundum core 
open at both ends. This should be about 12 inches 



Electric Furnaces 


161 


long and grooved like the other. You will need a 
somewhat longer length of Nichrome wire, enough to 
wind the core after it has been made into a coil as 
before. Seventy-five feet will be sufficient. After 
putting the coiled wire in place, cover it with Alundum 
cement and let it set. Be sure the ends of the wire 
are exposed for connections. Then set the core in¬ 
side a long cylindrical box and pack about it a mixture 
of the fire clay, asbestos fiber, and waterglass. Dry 
it with the heat of the electric current, and, after re¬ 
moving the core from the box, smooth off the outside 
with Alundum cement. Mount it on legs made of 
strap iron. 

The heat of this furnace will be too great for ordi¬ 
nary glass combustion tubing. A silica combustion 
tube will be required, and this you must obtain from 
a chemical supply house. It should be about 18 inches 
long. This furnace, too, will require no rheostat in 
series with it. It will take the place of the 4-tube 
burner and may be used for a number of important 
experiments. 

Preparation of Water Gas. —Throughout the mid¬ 
dle portion of the silica combustion tube put some 
pieces of charcoal. With rubber stopper, glass and 
rubber tubing connect to one end of the combustion 
tube a flask containing water and mounted on the ring- 
stand over the Bunsen burner. To the other end con¬ 
nect a delivery tube leading to inverted bottles of water 
in your pneumatic trough. The set-up aside from the 
furnace will be identical with that used in the prepara- 


162 The Boys Own Book of Science 

tion of hydrogen by passing steam over hot iron fil¬ 
ings. As the heat of the furnace comes up, bring the 
water in the flask to a boil and collect the gas which 
escapes from the delivery tube in the bottles. The 
bottles will at first be filled with a cloud of vapor, but 
this will soon disappear, and you will have a colorless 
gas. The hot carbon has taken the oxygen from the 
steam forming carbon monoxide and leaving the 
hydrogen of the water in the free state. The gas con¬ 
sists, then, of a mixture of carbon monoxide and 
hydrogen, both of which are combustible. 

To test the water gas invert one of the bottles upon 
the table and immediately apply a match. The gas 
will burn with the characteristic blue flame of carbon 
monoxide. Pour into the bottle a little limewater and 
shake it about. You will obtain a white precipitate 
showing that carbon dioxide has been formed in the 
combustion. A film of condensed vapor on the sides 
of the bottle will prove the presence of hydrogen in 
the gas. 

The preparation of hydrogen by passing steam over 
hot iron filings, already described in a previous chap¬ 
ter, may be carried out beautifully with this electric 
furnace. 

The preparation of copper oxide from short lengths 
of copper wire may be much more effectively done in 
this furnace than in the crucible type. Place the wire 
in the combustion tube and after bringing the furnace 
to a good heat pass over the wire a stream of oxygen 
from your generator. 


Electric Furnaces 


163 

Other uses of the furnace will suggest themselves. 
Quicklime may be made in it. But it is not best to 
prepare coke in it, for the soft coal swells in the pro¬ 
cess and it would be difficult to remove it from the 
tube. 






Chapter 19 

SOME METALS AND THEIR ALLOYS 

I AM not going to forget the fellow who cannot make 
an electric furnace. Many interesting experiments 
with metals and their alloys may be done with a Bun¬ 
sen burner or alcohol lamp. 

You do not need to be told that metals from 
earliest times have been among the most useful of the 
elements. Just as men have increased their knowledge 
of them, so has their mastery of Nature grown. Gold 
was one of the first metals known, doubtless because 
it occurs in the free state. Its metallurgy, the process 
of extracting it from the ore, is easy. And, if you 
have read history, you know that there was a long 
period of many centuries known as the bronze age. 
Primitive men first used implements of the chase and 
warfare fashioned from stone and flint. Then some 
cave man, raking over the embers of his dying fire, 
probably discovered shining globules of metal. With¬ 
out doubt they were copper or tin, for these metals are 
most easily reduced from their ores. At first this in¬ 
cident only aroused his curiosity. The bright metal 
appealed to his fancy, and he probably used it only for 
ornaments. Not for many years, possibly centuries, 
did it occur to him that this new material could be 
of any practical value. And quite likely a long period 

164 


Some Metals and Their Alloys 165 

elapsed before he made any deliberate attempt to 
duplicate the process, which he had accidentally dis¬ 
covered. Slowly he learned that these metals pos¬ 
sessed properties very much superior to those of stone 
and wood. From them he began to fashion crude 
weapons. How he blundered onto the fact that copper 
and tin together form an alloy surpassing in useful¬ 
ness either metal alone, we do not know. Painfully 
he forged ahead. At some time in the gray mists 
of antiquity, he discovered the metallurgy of iron, and 
then he began to dominate the earth. Today steel 
is the symbol of power. Because metals touch our 
lives at a thousand points, we should know something 
about them. 

What Are Metals? Chemically we distinguish be¬ 
tween metals and non-metals. A metal is an element 
whose oxide with water forms a base. A non-metal is 
an element whose oxide with water forms an acid. In 
addition metals have certain characteristic physical 
properties. In the pure state they have a high luster 
and are good conductors of heat and electricity. Many 
of them are tough and malleable. Some are brittle. 
Chemically metals vary from the intense activity of 
potassium and sodium to platinum and gold, which are 
little affected by the strongest reagents. Some will 
burn, others will not. Some melt at low temperatures, 
others only in the heat of the electric arc. 

Chemical Test for a Metal. —Cut a bit of sodium 
or potassium. Note its bright metallic luster and the 
rapidity with which it tarnishes. I hese are the most 


166 The Boys' Own Book of Science 

active metals known. So strong is their affinity for 
oxygen that they unite with it immediately upon ex¬ 
posure to the air and for that reason must be kept 
under kerosene. Throw the bit of metal upon some 
water in an evaporating dish. Nothing could illustrate 
better its very active nature than the ease with which it 
decomposes this very stable compound. Dip into the 
solution a piece of red litmus paper and note the deep 
blue color, showing the presence of a base. This is the 
test for a metal. 

As you know, limewater, which is slaked lime in 
solution, also turns red litmus blue. It contains in 
chemical combination the metal calcium. Sometimes 
the base of a metal such as that of iron is insoluble 
and will not change the color of litmus, but it will 
neutralize an acid to form a salt, and that test is 
equally good. 

Heating Metals in the Air. —In no other respect do 
metals exhibit more marked differences than in their 
behavior toward heat. Some metals burn, some oxi¬ 
dize, while still others are wholly unaffected. The 
very usefulness of metals depends upon these varying 
properties. 

Hold a piece of magnesium ribbon in the flame and 
note its brilliant combustion. At that temperature its 
affinity for oxygen is exceedingly strong. The product 
is a white powder that you can crush in your fingers. 
It in no way resembles the original substance. Then, 
if you have it, hold a platinum wire in the flame. It 
glows brightly, but that is all. When it has been re- 


Some Metals and Their Alloys 167 

moved and cooled, its properties are exactly what they 
were before. No chemical change has occurred. We 
might repeat the experiment and thus discover that 
the properties of metals differ widely under the in¬ 
fluence of heat. 

Does a Metal Grow Heavier, when Heated in the 
Air? Try it. Place in a porcelain crucible one or 
two grams of granular tin and exactly counterpoise it 
in your hornpan balance with lead shot. Then, plac¬ 
ing a clay triangle on the ring-stand support, mount 
the crucible over the Bunsen flame. As the tin melts, 
a dark scum will form on the surface. With an iron 
wire pull this to one side, thus exposing a fresh surface 
to the air. Again this scum will appear, and the process 
may be repeated over and over. Gradually you may 
change all of the tin into this gray powder. When you 
have done so, allow the crucible to cool and then re¬ 
place it in the balance. If you have been careful not 
to lose any of it, the powder will be considerably 
heavier than the original tin. It is no longer tin but 
tin oxide. And yet to understand the nature of this 
process required long years of patient experimentation. 
What is true of tin is true of all metals which will 
unite with oxygen. 

Making Solder.—Solder and pewter are two of the 
easiest alloys to make because lead and tin, from which 
they are prepared, have low melting points. Into a 
small but rather deep fire clay crucible weigh equal 
quantities of these two metals. Mount the crucible 
over the Bunsen burner and starting with a small flame 


168 The Boys' Own Book of Science 

gradually increase the temperature until all of the 
metal has melted down into a uniform mixture. 

For shaping these alloys into sticks, a plaster of 
Paris mold will be convenient. Make a mixture of 
plaster of Paris and water and fill with it a long nar¬ 
row box cover. While it is still soft, press into it 
two or three lead pencils. The molten solder may be 
poured into these depressions. When the sticks are 
hard, you may put them into small labeled specimen 
tubes and add them to your chemical museum. 

An Alloy that Melts in Hot Water. —An alloy that 
will melt in hot water used to be only a curiosity, but 
now it is of great importance for filling the perfora¬ 
tions in the pipes of automatic fire extinguishers of 
the sprinkling type. This alloy is known as Wood’s 
Metal and is made by melting together 80 g. of bis¬ 
muth, 40 g. of lead, 20 g. of tin, and 15 g. of cadmium. 

After the sticks of the alloy have hardened, heat 
some water in a beaker to about 70° C., and, holding 
one of the sticks with the tongs, thrust it into the 
water. It will quickly melt and run about the bottom 
of the beaker like mercury. Pour cold water into the 
beaker and the metal will immediately freeze. 

Such low melting point alloys are also used in mak¬ 
ing fuse wire for the protection of electric circuits. 

Lead is hardened for use in shot by alloying it with 
arsenic. Melt 100 g. of lead and while it is molten 
sift in a half gram of arsenic—not white arsenic but 
the element arsenic. Compare the properties of the 
alloy with that of soft lead. 




Melting an alloy in hot water heated over an alcohol burner. 


169 











Some Metals and Their Alloys 171 

Type metal, an alloy which has the peculiar prop¬ 
erty of expanding upon solidification, may be prepared 
by melting together 75 g. of lead, 20 g. of antimony, 
and 5 g. of tin. 

You may galvanize iron by dipping it into molten 
zinc. Clean a large “cut” nail by heating it to as 
high a temperature as possible in your Bunsen burner, 
allowing it to cool, and dipping it in hydrochloric acid. 
Then scour it with sand, wash it off, and reheat. While 
it is still hot, dip it into olive or cotton-seed oil and 
then into a crucible containing molten zinc. Upon re¬ 
moving and cooling you will find that the iron has been 
galvanized. 

By cleaning sheet iron and dipping it into molten 
tin, tin plate may be prepared in a similar way. 

Home-made thermit will alford you one of the most 
interesting and spectacular demonstrations that can 
be performed with metals. As you may know, thermit 
is the trade-name of a mixture which gives one of 
the highest temperatures known to science. Its 
great use is in welding iron and steel. Its ignition 
gives liquid iron at a temperature of more than 
3000° C. 

Mix about equal quantities of aluminum dust and 
ferric oxide. Place a considerable quantity of the mix¬ 
ture in a small dish made of thin sheet iron, or in a 
small tin basin. Prepare some ignition powder by 
mixing equal parts of magnesium dust and powdered 
potassium chlorate. In a little depression hollowed 
out of the top of the heap of thermit place a half tea- 


172 The Boys Own Book of Science 

spoonful of the Ignition powder and insert in it a 
short length of magnesium ribbon (F’ig. 21). 

Place the dish and mixture on a tripod support set¬ 
ting in a box containing an inch layer of sand. Light 
the magnesium ribbon and very quickly the reaction 
will spread throughout the mass of powder, producing 
a light of dazzling brilliancy and liberating white-hot 



Figure 2 1. 

A mixture of thermit ready for ignition. 


molten iron, which will melt a hole through the iron 
dish and flow like lava into the sand box below. 

In this experiment it is well to protect your eyes 
with colored glasses . 

If you can find a 2-inch length of hollow tiling about 
an inch and a half in diameter, rest it upon a thick 
sheet of soft iron or steel and fill it with a fresh mix¬ 
ture of thermit, with the ignition powder and fuse at 
the top. Upon ignition you will obtain a well of 
molten metal which will fuse with the iron beneath 









Some Metals and Their Alloys 173 

and weld itself to it. When the mass has cooled, 
break away the tile and you will find that the “boss” 
of iron cannot be removed by the most vigorous 
hammering. 

Thermit is very widely employed for welding broken 
parts of locomotives, street car rails, propeller shafts, 
and any of the other multitudinous breaks in iron and 
steel. If you do not wish to prepare it, real thermit 
and ignition powder may be purchased from a chemi¬ 
cal supply house. 

The “Alchemy” of Metals. —To the alchemist the 
transformation of one metal into another seemed a 
simple thing. He thrust a bar of iron into a solution 
of blue vitriol and behold presently he had copper. To 
him, ignorant as he was of real chemical processes, it 
seemed perfectly plain that the iron had been changed 
into copper. But we know now that some metals will 
replace others from their solutions. That is because 
some metals are more active than others. In fact all 
the metals may be arranged in an order such that any 
one of them may be replaced from its solution by any 
metal preceding it and it will replace any metal follow¬ 
ing it. 

In two sets of cylinders or tall test tubes place 
fairly strong solutions of the nitrates of zinc, lead, 
copper, mercury (either mercurous or mercuric), and 
silver. Cut some long narrow strips of sheet zinc and 
thin copper foil. Into one of the two sets of test tubes 
containing these solutions thrust strips of zinc and 
into the other strips of copper. Almost immediately 


174 The Boys Own Book of Science 

the action will begin, but you will not obtain deposits 
in every case. Note carefully those in which you do. 
Of course zinc will not replace itself in zinc nitrate, 
but in the case of all the other metals you will obtain 
a deposit, showing that of this group zinc is the most 
active. In the course of a half hour you will observe 
that the copper solution (copper sulfate may be sub¬ 
stituted for the nitrate) has been decolorized and that 
a heavy deposit of metallic copper has formed in the 
test tube. The copper may be dark from impurities 
in the zinc, but you may melt it in your electric furnace 
into a metallic button. Of course at the same time 
that the copper is replaced the zinc goes into solution. 

Examine the strip of zinc placed in the solution of 
mercury. Rub it and note the silver luster. Break 
the strip and examine the broken edge. The zinc is 
now brittle and the edge is white clear through, show¬ 
ing that the mercury from the solution has penetrated 
the metal. 

Remove the spongy deposits of silver from the two 
test tubes containing solutions of this metal and rub 
them on a glass plate. The bright luster of the white 
metal will be obtained. You may redissolve the metal 
in nitric acid and obtain silver nitrate again. 

Pure Silver from a Silver Coin.— Dissolve a small 
silver piece in not too dilute nitric acid. You will ob¬ 
tain a solution with a blue color, due to the presence 
of copper, for to harden coin metal an alloy of about 
92 per cent silver and 8 per cent copper is employed. 
Your solution will contain both silver nitrate and 



Some Metals and Their Alloys 175 

copper nitrate. The problem is to separate pure me¬ 
tallic silver from the solution. The preceding work 
on the replacement of metals will enable you to do this. 
No doubt some of you see the method already. All 
you need to do is to insert a metal that will displace 
the silver but not the copper. Zinc cannot he used, 
for it will displace the copper as well as the silver. 
But how about copper itself? You have just seen that 
copper will drive out silver from its solution, but of 
course it cannot displace itself. 

Thrust a strip of copper into the solution and allow 
it to remain until you are sure all of the silver has been 
displaced. Remove the copper and scrape all the 
silver off onto a filter paper placed in your funnel. 
Into a clean beaker pour off the clear copper nitrate 
solution, leaving in the bottom any sediment that may 
be left. This sediment will of course be silver. Throw 
it upon the filter paper with the rest of the silver, 
using distilled water to remove the final portions. Now 
wash the silver by passing distilled water through the 
filter for some time. Use only small amounts of water 
at a time, and, if you wish perfectly pure silver, con¬ 
tinue to wash it until the wash water that comes 
through the filter will give no blue color when a few 
drops of ammonia water are added to it. You may 
melt this silver down into a small button in your elec¬ 
tric furnace, or redissolve it in nitric acid and obtain 
a solution of pure silver nitrate. If you wish to ob¬ 
tain crystals of silver nitrate, evaporate off part of the 
water and allow the rest of the solution to cool. 


176 The Boys Own Book of Science 

By a similar process of crystallization you may 
separate the copper nitrate. 

The principles involved in this replacement of metals 
are at the bottom of a great deal of chemical work. 
The chemical action of electric cells and the electroly¬ 
sis of metals are examples. 


Chapter 20 


JUSTUS VON LIEBIG 

C oming upon the scene a little later than Berzelius 
and extending his period of service just a quarter 
of a century longer was Justus von Liebig, a great 
German chemist. He was an old autocrat and made 
many enemies as well as warm friends. As a lad he 
was apprenticed to an apothecary, and apothecary 
shops in those days were small research laboratories, 
that is, laboratories in which original experiments and 
discoveries were made. Liebig's bent, like Davy’s, 
seemed to be for making explosives. One day young 
Liebig saw some traveling showmen prepare fulminate 
of silver, a very explosive compound. This of course 
appealed tremendously to the fancy of the young ex¬ 
perimenter, and he immediately attempted to dupli¬ 
cate the process. The result was a terrific explosion 
which tore a hole through the roof of the apothecary 
shop and blew Liebig out of the drug business, for his 
employer dismissed him forthwith. 

But Liebig had enjoyed too much of the pleasures 
of chemistry to permit his fondness for experimenting 
to be thus rudely destroyed. Therefore he asked his 
father to send him to a university where he might study 
chemistry to his heart’s content. His father consented 

177 


178 The Boys ' Own Book of Science 

and off he went, first to a German university and then 
to Paris. At Paris he studied in the laboratory of 
Gay-Lussac, a famous French chemist, just as others 
had studied with Berzelius. 

Returning to Germany, Liebig established the 
world’s first college laboratory for actual instruction 
in chemical work. Students flocked to him from every 
part of Europe and America. And he was a wonder¬ 
ful teacher. Some of the most distinguished chemists 
of the last century were his pupils. 

Liebig invented new processes of organic analysis. 
He founded the science of agricultural chemistry, and 
among his discoveries of new compounds is that of 
chloroform. And possibly it should be mentioned that 
“Liebig’s Beef Extract” is a product of his creation. 
It was the happy fortune of Liebig to live and work 
in the days when chemistry was in its youthful prime, 
and he made the most of his opportunity. 


Chapter 21 


MORE ABOUT THE CHEMISTRY OF 

COMBUSTION 

P ROBABLY your definition of combustion would be 
the chemical union of oxygen with a substance 
to produce heat and light. But we may have com¬ 
bustion without oxygen. Any chemical change accom¬ 
panied by light is a form of combustion. If there is 
light there will always be heat. In fact there can be 
no chemical change without the giving off or the ab¬ 
sorption of heat. But can there be combustion with¬ 
out a flame? Your first impulse will be to say “No.” 
A little reflection will show you that there may be. 
The term flame is the name we give to the combustion 
of two gases or of a gas and a vapor. A vapor is the 
gaseous product obtained from a substance which at 
ordinary temperatures is a liquid or a solid. 

Combustion without a flame.—Place a little sulfur 
in the bottom of a test tube and bring it to a boil in 
the flame. When the hot sulfur vapor is issuing from 
the tube drop into it a strip of thin sheet copper or 
some fine copper wire. You will note that the copper 
glows brightly. It burns, but there is no flame. When 
the test tube has cooled, remove the strip. It is no 

longer metallic copper. Its bright luster is gone. It 

179 


i8o The Boys’ Own Book of Science 

is no longer flexible. You can break it easily in your 
fingers. You now have a bluish-black substance called 
copper sulfide. In the union of the copper there were 
heat and light, but no flame. 

Mix one part of iron filings with twice that bulk of 
finely powdered sulfur. Place this mixture in a test 
tube and heat in the flame until the contents of the tube 
begins to glow. Withdraw the test tube and note that 
the combustion which has started spreads throughout 
the whole mass. Again you have combustion, but no 
sign of a flame. 

Mix thoroughly equal parts by volume of finely 
powdered sulfur and zinc dust. Place this mixture 
upon a square of asbestos board and ignite it by throw¬ 
ing the Bunsen burner flame down upon the heap. You 
will obtain a vivid combustion and, it may seem, a 
flame, but there is none. 

Prepare a bottle of oxygen and thrust into it with 
your deflagrating spoon a glowing piece of charcoal. 
The glowing will be much more brilliant, but you can¬ 
not detect a flame. Repeat the burning of steel wool 
in oxygen and try to observe a flame. Even in the very 
vivid combustion of magnesium ribbon or flash powder, 
there is no true flame. 

Mix thoroughly equal parts of copper oxide in pow¬ 
dered form and finely powdered charcoal. Place them 
in a hard glass test tube fitted with a one-hole stopper 
and delivery tube. Shake the tube so that the mixture 
becomes spread out somewhat in a thin layer and clamp 
it to your ring-stand in a nearly horizontal position. 


More About the Chemistry of Combustion 181 

Let the delivery tube dip into a test tube containing 
a little limewater. Then heat the mixture. Carbon 
dioxide will be driven off which may be detected by 
the white precipitate obtained in the limewater. After 
a short time, as you strongly heat the tube, the mixture 
will begin to burn and a bright glow will spread 
throughout the mass. Combustion is taking place. 
The copper oxide is giving up its oxygen to the char¬ 
coal so rapidly that it is being heated to incandescence. 
But you see no flame. 

There are other illustrations of combustion with¬ 
out a flame but these are sufficient to demonstrate the 
point. 

The Bunsen Burner Flame.—Light your Bunsen 
burner and open the air holes at the bottom of the 
tube. Note that the flame consists of two cones—an 
inner and an outer. There is really a third consist¬ 
ing of an invisible envelope of burned gases surround¬ 
ing the other two. The inner cone consists of un¬ 
burned gas, cool at the bottom but reaching a tempera¬ 
ture at the tip way above its kindling point. To show 
that the gas in this cone is not burning, quickly thrust 
into it at the bottom a match head. The match will 
not ignite, and you may carefully raise it nearly to the 
tip of the cone before it will do so. Holding a glass 
tube in a nearly vertical position thrust it into this 
inner cone and light the gas as it escapes from the 
upper end. The tip of this inner cone is called the 
reducing flame because the hot unburned gas in it has 
a great affinity for oxygen and, if thrown upon a me- 



182 The Boys' Own Book of Science 

tallic oxide, will reduce it. The gas in the outer cone 
is vigorously combining with oxygen and this portion 
is known as the oxidizing flame. As we shall see, both 
of these flames have important uses in chemical 
analysis. 

Burning Air.—We usually think of air as the sup¬ 
porter of combustion and gas as the combustible sub¬ 
stance. You will recall, too, that hydrogen will burn, 
although a lighted candle thrust up into an inverted 
bottle of the gas will go out. Still these terms—sup¬ 
porter of combustion and combustible substance—may 
be inverted. We may burn air in an atmosphere of 
illuminating gas. 

Fit a lamp chimney with a 2-hole stopper carrying 
a glass elbow and a straight glass tube about i centi¬ 
meter in diameter and reaching well up into the chim¬ 
ney. Connect the elbow with the gas supply and over 
the top of the chimney place a piece of asbestos hav¬ 
ing a hole in the center. Placing your hand on the 
top of the asbestos, turn on the gas and light it at the 
lower end of the straight glass tube. Immediately 
remove your hand and light the gas at the top of the 
chimney too. As you do so, you will observe that the 
flame passes from the bottom of the tube to the top 
and continues to burn inside the chimney (Fig. 22). 
Air drawn in at the bottom of the tube is burning in an 
atmosphere of illuminating gas. In this case the air 
is the combustible substance and the illuminating gas 
the supporter of combustion. 


More About the Chemistry of Combustion 183 

Protecting Gas from Ignition.—With the tongs 
hold a 4-inch square of rather fine mesh iron or copper 
gauze about 3 inches above the Bunsen burner. Turn 
on the gas and light it above the gauze. You will find 
that, while the gas will burn above the gauze, the flame 
will not strike down through and ignite the gas below. 
This is because the metal is a good conductor of heat. 



Figure 22 . 

Apparatus for burning air in an atmosphere of illuminating gas. 

It distributes the heat over so large a surface that the 
gas cannot be brought to its kindling temperature. 

This is the principle employed so successfully a cen¬ 
tury ago by Sir Humphry Davy in his invention of the 
miner’s safety lamp. He surrounded the naked flame 
with a cylinder of copper gauze. When the miner 
enters a region containing the dangerous mixture 
known as “fire damp,” the explosive gases penetrate 
the gauze causing a series of small explosions and thus 















184 The Boys’ Own Book of Science 

give a warning which leads him to beat a retreat. The 
gauze does not permit the flame to pass through and 
ignite the gas outside. Thus explosions, which would 
wreck the mines, are frequently prevented. 

You Can Easily Make a Safety Lamp.—Roll a sheet 
of fine iron or copper gauze into the form of a cylinder 
and fasten it along the edges. By means of wire sup¬ 
ports secure a candle in one end and light it. Now 
holding the cylinder in a nearly horizontal position 
over the Bunsen burner, turn on the gas, but the 
burner will not light. The gas will pass through and 
burn on the inside of the cylinder, but there will be no 
flame on the outside. 

In order that a gas may undergo combustion a cer¬ 
tain definite temperature, called the kindling tempera¬ 
ture, must be reached. 

Another very striking experiment to illustrate this 
principle may be shown with a funnel, a square of 
gauze, and some gunpowder. Clamp the funnel stem 
down to the ring-stand support and connect it to the 
gas supply. Place over the mouth of the funnel a 
fine mesh gauze and place in the center of it a little 
heap of gunpowder, being careful not to let it spread 
out very far. Turn on the gas and light it. You will 
have the quite startling spectacle of gunpowder being 
immersed in the heart of a flame and yet unable to 
burn (Fig. 23). 

An Acetylene Lamp.—You may make a lamp for 
studying the combustion of acetylene gas and also 
obtain a beautiful and useful light by putting together 



Burning air in an atmosphere of illuminating gas. Gas is burning at the top 
of the chimney and a small jet of air inside the chimney. 


185 

















More About the Chemistry of Combustion 187 

the following materials—a wide-mouth bottle of about 
2 quarts capacity, a good-sized lamp chimney with 
straight sides and constriction toward the bottom, 
small disk of coarse gauze, one-hole rubber stopper, 
6-inch length of glass tubing, rubber connection and 
pinch cock, acetylene gas tip, and 18 inches of heavy 
aluminum wire. 



Figure 23. 

Gunpowder enveloped in flame but still not burning. 

Make a wire support for the chimney and mount 
it in the bottle with the upper end projecting a little 
distance above the top. Fit the constriction in the 
chimney with the gauze disk. Fill the chimney two- 
thirds full of lumps of calcium carbide. Insert in the 
stopper the length of glass tubing and attach to it the 
rubber connection, gas tip and pinch cock. Now fill 
the bottle nearly full of water and open the pinch cock 
(Fig. 24). The water will slowly rise into the chim- 













188 


The Boys’ Own Book of Science 

ney and coming in contact with the carbide will gener¬ 
ate acetylene gas. Gradually the air will be driven 
from the chimney and the gas jet may be lighted. You 
will obtain a soft white light of great brilliancy. 

Smoke Rings.—The production of a gas that will 



Figure 24. 

An acetylene lamp. 


undergo spontaneous combustion the instant it comes 
in contact with the air will make a very spectacular 
demonstration. Incidentally you will be able to ob¬ 
tain with it some of the prettiest smoke rings that 
were ever formed. 

In a small flask put from 200 c.c. to 300 c.c. of a 


























More About the Chemistry of Combustion 189 

strong solution of either sodium or potassium 
hydroxide. Into the neck of it fit two angle tubes, 
one reaching just through the stopper and the other 
extending nearly to the bottom of the flask. Mount 
the flask on a ring-stand over the Bunsen burner. 
Put into the solution a piece of yellow phosphorus 
about as large as a pea. (Remember that phos¬ 



phorus must not be touched with the fingers and 
that it must be cut under water.) To the angle tube 
passing beneath the surface of the solution in the flask 
connect the supply of illuminating gas and to the other 
attach a delivery tube, the bent up end of which dips 
beneath the surface of water in a large basin. (Fig. 

2 5 ‘) . . . 

First open the gas cock and allow the illuminating 
gas to sweep the air from the flask. Then light the 



























190 The Boys’ Own Book of Science 

Bunsen burner and bring the solution to a boil, keep¬ 
ing the end of the delivery tube under the surface of 
the water in the basin. When the solution is boiling 
vigorously, turn off the gas and watch the bubbles rise 
through the water in the basin. In a few moments 
they will spontaneously ignite and, as each bubble does 
so, a beautiful smoke ring will form and slowly rise 
in an ever expanding circle to the ceiling. 

A beautiful green flame may be produced by the 
combustion of 20 c.c. of alcohol containing 3 g. of 
borax and 3 c.c. of concentrated sulfuric acid. Put 
the mixture into a flask provided with a one-hole stop¬ 
per and short length of glass tubing. Mount the flask 
over the Bunsen burner and clamp just above the 
stopper a 2-inch length of combustion tubing. Boil the 
mixture in the flask and ignite the vapor that issues 
from the tube. It will burn with a green flame. 

Fire Extinguishers.—One of the most difficult prob¬ 
lems connected with combustion is to find efficient 
means of stopping the process when it gets beyond 
our control or starts by accident. 

Into the bottom of a beaker put a teaspoonful of 
baking soda and pour upon it a little acid. Any acid 
may be used, or even vinegar. Into the gas that 
bubbles up and fills the beaker thrust a lighted match. 
It at once goes out. The carbon dioxide that envelops 
it will not support combustion. 

Into an evaporating dish pour a little carbon 
tetrachloride, or “Pyrene.” Heat it over the flame 
and thrust into the heavy vapor that forms a lighted 


More About the Chemistry of Combustion 191 

match. Again, robbed of oxygen, the flame goes out. 
Carbon dioxide and carbon tetrachloride are two of 
the most efficient agents used in fighting fire. 

Put a teaspoonful of gasoline into an evaporating 
dish and light it with a match. Pour a little water 
on it, but note that the flame is not extinguished. The 
gasoline being lighter than the water floats upon its 
surface and continues to burn. Now pour a little 
carbon tetrachloride into the dish and the flame will 
quickly go out. This liquid vaporizes and surrounds 
the flame with a heavy blanket of incombustible gas 
and one which will not support combustion. 

Making a Fire Extinguisher.—Fill a test tube two- 
thirds full of a saturated solution of baking soda. (A 
saturated solution is made by dissolving in a liquid 
all of the finely pulverized substance that it is possible 
to make it hold. It is often a good plan to stir a con¬ 
siderable quantity of the substance into the hot liquid 
and then cool the solution. If some of the substance 
separates out on cooling, the solution is saturated.) 

In this solution float a small pill bottle containing a 
little concentrated sulfuric acid. Fit the neck of the 
test tube with a one-hole stopper carrying a glass 
elbow. Quickly invert the tube spilling the acid into 
the solution and immediately there will be a rapid 
rush of gas and froth through the exit tube. The gas 
is carbon dioxide, and, if the delivery tube is directed 
toward a lighted candle, the flame will be extinguished. 

A larger fire extinguisher may be made in a similar 
way using a pint bottle. Fill the bottle two-thirds 


192 The Boys’ Own Book of Science 

full of bicarbonate solution (baking soda) and place 
a dilute solution of the acid in a test tube so resting in 
the bottle that its mouth is not submerged (Fig. 26). 
To the exit tube attach a rubber connection carrying 
a jet tube at the end. Leave a good sized opening at 
the end of the jet tube. Upon inverting this a vigor¬ 
ous flow of carbon dioxide will be obtained. 



A fire extinguisher. The bottle contains a saturated solution of baking 
soda and the test tube moderately strong sulfuric acid. 

9 

A Carbon Dioxide Trick.—Arrange a generator for 
producing carbon dioxide from marble and hydro¬ 
chloric acid, just as you did in the chapter on the 
Atmosphere. Get the generator into action and let 
the delivery tube pass to the bottom of a wide mouth 
bottle placed upright on the table (Fig. 27). Since 
carbon dioxide is heavier than air, it will settle in the 
bottle and displace the air which originally filled it. 






















More About the Chemistry of Combustion 193 

Have at hand a short candle to which you have at¬ 
tached a stout wire so bent that you can raise and lower 
the upright flame in the bottle. You can tell how full 
of carbon dioxide the bottle is at any time by lowering 
the lighted candle into it. The flame will be ex- 



Convenient form of apparatus for the preparation and collection of carbon 
dioxide. The chimney contains marble chips resting on a perforated lead 
disk, and in the bottle is dilute hydrochloric acid. 

tinguished at the level of the gas. And here is the 
trick. If, just as the flame begins to go out and 
apparently does so, you will quickly raise the candle the 
flame will reappear. A little practice will enable you 
to do this beautifully. The explanation is this. A 
tiny almost colorless flame still burns just at the level 
of the carbon dioxide and is connected with the wick 
































194 The Boys’ Own Book of Science 

by an invisible column of still hot incandescent vapor. 
Upon quickly raising the candle this vapor burns and 
relights the wick. 

A more striking demonstration of the fire extin¬ 
guishing properties of carbon dioxide may be shown 
in the following way. Make a small trench about 18 
inches long and 3 inches deep by folding a piece of 
sheet zinc trough shaped. Set in the bottom of this 
a row of Christmas candles. Soften the bottoms of 
the candles and they will adhere to the zinc upon 
cooling. 

Start your generator and fill a quart bottle with car¬ 
bon dioxide by displacement of air, as before. Raising 
one end of the trench on a small block, light the candles 
and quickly pour down it the bottle of gas. One after 
another the candles will be extinguished. This in¬ 
teresting experiment illustrates several properties of 
this gas. It is heavier than air. It does not support 
combustion. It is incombustible. 

Carbon monoxide, an important constituent of a 
number of fuel and illuminating gases, may be pre¬ 
pared by the action of concentrated sulfuric acid on 
formic acid. ( Since this gas is poisonous he careful 
not to breathe it.) 

The apparatus for the preparation of this gas is 
exactly the same as that for hydrogen. Pour through 
the thistle tube a little formic acid. Be sure that the 
thistle tube dips beneath the surface of the liquid in 
the generator. Then add to the contents of the 
generator some concentrated sulfuric acid. A gas will 



Extinguishing candles by pouring carbon dioxide upon them. 


195 













More About the Chemistry of Combustion 197 

at once begin to escape which may be collected oyer 
water. 

Remove a bottle of the gas and present the mouth 
of the bottle to the Bunsen flame. A blue flame will 
fill the bottle showing the combustible nature of the 
gas. Shake a little limewater in the bottle and the 
white precipitate will show that carbon dioxide is the 
product of the combustion. This is the gas that burns 
with a blue flame when you open the furnace door 
shortly after fresh coal has been put on the fire. It 
is also the poisonous gas which issues from the exhaust 
of an automobile engine when it is run in a closed 
garage where the supply of air is insufficient for com¬ 
plete combustion of the gas. 

Producer gas, one of the most important fuel and 
power gases, consists principally of carbon monoxide. 
If you have made an electric furnace of the combus¬ 
tion type, fill the silica tube with small pieces of char¬ 
coal and connect to one end of it a carbon dioxide 
generator. To the other end connect a delivery tube 
and arrange a pneumatic trough with inverted bottles 
of water. Bring the charcoal to a good heat and pass 
over it a slow stream of carbon dioxide. To do this 
use in the generator dilute acid and only a little at 
a time. Collect in the bottles the gas that escapes 
from the tube. 

Remove one of the bottles and apply a match to the 
gas. It burns with a blue flame showing that the car¬ 
bon dioxide has been reduced to the monoxide. This 
is essentially what happens in a gas producer. Like- 


198 The Boys' Own Book of Science 

wise in a furnace carbon dioxide forms in the bottom 
of the fire-pot and is reduced by the fresh coal on top. 

Carbon monoxide is the gas which often kills people 
in poorly ventilated sleeping rooms. Fresh coal is 
put on the fire at night and the dampers nearly closed. 
Possibly, too, the lids are partly removed to keep the 
fire from burning out. Here are just the conditions 
for the production of this deadly gas, which is all the 
more dangerous because it is odorless. 

The Flashing Point of Kerosene.—Place 2 or 3 
tablespoonfuls of kerosene in an evaporating dish and 
remove the kerosene container to a safe distance. Try 
to light the kerosene with a match. If it is of good 
quality, you will not succeed. Very gently warm the 
mixture with a small flame and at frequent intervals 
apply a match to the vapor. With a thermometer take 
the temperature of the liquid and note the point at 
which the vapor just ignites. This is the flashing point 
or very nearly it. If the vapor continues to burn, you 
have passed the point. In that case put out the burner 
flame and allow the kerosene to cool. Every minute 
or two test with a lighted match. The temperature at 
which the vapor will just light is the flashing point. 
It should lie between 120° F. and 140° F. This point 
is the most important indication as to the quality of 
this liquid fuel. 

Fireproofing Cloth.—Make a solution of 16 g. of 
alum, 3 g. of boric acid, 5 g. of ammonium carbonate, 
and 3*5 g- of borax in 100 c.c. of water. Dip into it 
a strip of muslin and let it dry completely. Try to 



More About the Chemistry of Combustion 199 

burn it, and compare the rate at which it burns with 
that of muslin not so treated. 

Making a Safety Match.—Make a mixture of 4 
drops of thin glue, one-fourth as much red phosphorus, 
and as much finely pulverized sand as phosphorus. 
Spread the mixture in a thin layer on a piece of paste¬ 
board, and allow it to dry for a day. 

In the meantime whittle out some match sticks. 
Melt some paraffin and soak the ends in it. Make a 
mixture of 3 drops of thin glue, twice as much pow¬ 
dered potassium chlorate, and one-third as much pow¬ 
dered antimony sulfide. Dip the sticks into the 
mixture and then let them dry for several hours. When 
they are dry, you will be able to light them by rubbing 
on the prepared surface. 

In this chapter we have described only a few of 
the many experiments on combustion which may be 
performed, but they are sufficient to give you a fairly 
broad understanding of this important chemical 
process. 


Chapter 22 


JOSEPH HENRY 

N OT all of the distinguished scientists who started 
as home-laboratory workers became chemists. 
One of the earliest and most eminent of America’s 
scientific men was the physicist Joseph Henry. He was 
born near Albany, New York, in the year 1799. His 
first ambition was to become an actor, but one day he 
chanced to read a book on science, which he ever after 
said changed the whole course of his career. He at 
once determined to devote his life to scientific work. 
To obtain the necessary education Henry attended the 
Albany Academy, and, to pay his expenses, he taught 
school at intervals. After a time he was engaged to 
survey the route for a new highway through the un¬ 
tracked forests of the Empire State. Tie did it during 
the dead of winter, amid deep snows and often exposed 
to the danger from wild beasts. So interesting did 
this work seem to him that he was about to accept 
another engineering contract when he was offered the 
position as professor of physics at the Albany 
Academy. This decided his future, and fortunate it 
was for the cause of science in America. 

Henry plunged into his new duties with enthusiasm, 
and immediately he began to experiment in every 

spare moment. Much of his work was original, and 

200 


201 


Joseph Henry 

all of it was new to him. Particularly did he dis¬ 
tinguish himself in the field of electricity. Independ¬ 
ently of any knowledge of Faraday’s discoveries with 
induced currents and anticipating him in many of them 
Henry covered the same ground. Sturgeon in Eng¬ 
land had just invented the electromagnet and Henry 
determined to try out the possibilities of this new de¬ 
vice. Going to a blacksmith-shop he obtained a rod 
of soft iron bent into the shape of a horseshoe. Not 
finding any wire suitable to his purpose, he invented 
silk-covered magnet wire. Then he wound upon this 
soft iron core 9 lengths, each 60 feet long, of fine in¬ 
sulated copper wire, arranged so that he could con¬ 
nect them in any desired manner. With this little 
giant and a cell containing only a half pint of acid and 
one-fifth of a square foot of metal surface, Henry 
lifted masses of iron weighing from 60 to 650 pounds. 
With a tiny cell having plates only one inch square, he 
lifted 85 pounds. For Yale and Princeton universi¬ 
ties he constructed large magnets capable of lifting 
considerably more than a ton. Henry also invented 
the relay, without which telegraphy would have been 
impossible. Through a mile of wire strung back and 
forth across his laboratory he actually sent and re¬ 
ceived signals. 

Later Henry became professor of physics at Prince¬ 
ton University and was made first secretary of the 
Smithsonian Institution in Washington. And all of 
this and much more came from a boy’s early desire to 
experiment. 


Chapter 23 
FIREWORKS 

1 PRESUME no other part of chemistry appeals to the 
beginner more strongly than spectacular displays of 
fireworks. You will wish to celebrate the Fourth of 
July with plenty of light and noise, and yet do so with¬ 
out danger to yourself. I will try to show you how 
this may be done. 

Touch Paper.—In igniting some of the mixtures 
which I shall describe you will need fuses. Touch 
paper is ideal for this purpose. It is prepared by 
soaking strips of filter or blotting paper in a strong 
solution of potassium nitrate (saltpeter) and allow¬ 
ing them to dry. This paper will burn without a flame, . 
just as a fuse does, and the fire cannot be extinguished 
by blowing. 

White Fire.—Mix together equal quantities of pow¬ 
dered potassium chlorate and magnesium dust. Use 
about two teaspoonfuls of each. Place the mixture on 
a square of asbestos board, or a block covered with as¬ 
bestos paper, and ignite it with a long wax taper. 
Never use a match. The combustion comes with great 
suddenness and gives a flash of blinding light and a 
dense cloud of smoke. At night it is of wonderful 

brilliancy. This mixture is commonly called flash 

202 


Fireworks 


203 


powder, so much used in taking indoor photographs. 
The light is particularly rich in the chemical rays that 
affect a photographic plate. 

Red Fire.—Mix 1 g. of powdered potassium chlo¬ 
rate with 11 g. of strontium nitrate. If these sub¬ 
stances are not already powdered, pulverize them 
separately and then mix them. Never pulverize them 
together. Stir into this mixture 4 g. of finely pow¬ 
dered sulfur and J 4 g. of lampblack. Make a cone- 
shaped heap of the mixture on an asbestos square and 
insert in the top a piece of fuse paper. Ignite the fuse 
and the mixture will burn with an intensely red flame. 

Green Fire.—This time mix 3 g. of pulverized po¬ 
tassium chlorate with 8 g. of powdered barium nitrate 
and 3 g. of powdered sulfur. Again do not pulverize 
the chlorate and nitrate together. Using a fuse of 
touch paper ignite the mixture. It will give a brilliant 
green light. 

Purple Fire .—Separately pulverize 2 g. of copper 
sulfate (blue vitriol), 2g. of sulfur, and 15 g. 
of potassium chlorate. When ignited with touch 
paper, a purple fire is produced. 

Blue fire may also be obtained from a mixture of 
2 g. of pulverized charcoal, 2 g. of cupric chloride, and 
4 g. of potassium chlorate. 

The National Colors.—Try at night the ignition of 
a mixture of the materials used in red fire, white fire, 
and blue fire. 

Igniting flash powder by electricity is an interest¬ 
ing and safe method to use. Cover a board 6 inches 



204 


The Boys’ Own Book of Science 

square with asbestos paper. Along the middle line 
about 3 inches apart drive two nails, leaving an inch 
of each above the board. If you like, you may insert 
brass binding posts instead of the nails. Between the 
nails connect a piece of No. 30 iron wire, or any other 
piece of very fine iron wire which you may have. Over 
the wire place in a heap the mixture of powder which 
you wish to ignite. Off at some distance, 4 or 5 feet, 
place a half dozen good dry cells. Connect them 
through a switch to the ends of the iron wire on the 
ignition block. Then close the circuit. The electric 
current will heat the iron wire to incandescence and 
set off the powder. 

Old-fashioned Gunpowder.—Before the invention 
of the powerful explosives of modern times, gun¬ 
powder consisted of a mixture of charcoal, sulfur, and 
saltpeter. Here were two easily combustible sub¬ 
stances and a strong oxidizing agent. Furthermore 
the products of the combustion were chiefly gases and a 
large quantity of heat, just the combination needed for 
an explosive. 

To prepare this powder make a mixture of 30 g. of 
finely pulverized potassium nitrate and 5 g. each of 
powdered charcoal and sulfur. Ignite it with a long 
wax taper. It will burn readily giving a dense cloud 
of smoke, and the unavoidable smoke was the great 
objection to this kind of powder. In addition, the 
oxygen necessary for the combustion must come from 
particles outside the charcoal and sulfur. In modern 
high explosives the molecules of the explosive com- 




Throwing the switch for the ignition of flash powder, 
resistance is being used. 


A no-volt circuit with no 


205 













Fireworks 


207 


pound contain the oxygen necessary for their own com¬ 
bustion. I his results in a much quicker and a vastly 
more violent explosion. 

Making a Sparkler.—In a small test tube melt some 
potassium chlorate. When it has cooled to a solid 
mass, break away the glass. Rub this stick on the 
ignition surface of a safety match box. A shower of 
sparks will result. 

Combustion of Sugar and Potassium Chlorate.— 
Carefully mix without friction equal quantities of 
finely powdered potassium chlorate and granulated 
sugar. Place the mixture on the asbestos square and 
by means of tongs drop upon it a piece of asbestos 
paper saturated with the strongest sulfuric acid. A 
very rapid combustion and an intensely blue flame will 
result. 

Combustion of Aluminum Dust and Bromine.— 
Clamp a test tube in a vertical position on your ring- 
stand and place in it a small quantity of aluminum dust 
or filings. Heat the bottom of the tube until the 
glass is just red. Then from a medicine dropper let 
fall upon it 10 drops of bromine. A very vivid com¬ 
bustion results. 

After the contents of the tube has cooled let 2 or 3 
drops of water fall into it. You will obtain another 
vigorous action and a hissing sound. (For this ex¬ 
periment a hard glass test tube is best.) 

Combustion of Aluminum Dust and Iodine.—The 
previous experiment may be repeated with iodine, 
which will be more easily obtained. Heat the alumi- 


208 


The Boys’ Own Book of Science 

num to faint redness in a hard glass test tube and drop 
upon it from a folded paper a half gram of finely 
powdered crystals of iodine. The combustion is even 
more vivid than it is with bromine, and, if a Bunsen 
burner flame is quickly held to the mouth of the tube, 
the product of the combustion itself will take fire. 

Combustion of Zinc Dust.—Mix 8 parts of am¬ 
monium nitrate with i part of ammonium chloride. 
Spread this out in a thin layer on a plate of glass and 
cover it with a layer of zinc dust. Let fall upon the 
mixture a single drop of water and combustion will 
take place. 

A Gas Explosion.—But I hear you asking, “Where 
is the noise?” A Fourth of July celebration would 
surely be a fizzle without an explosion. The follow¬ 
ing perfectly harmless demonstration will provide you 
noise in abundance. Obtain a gallon can having one 
hole in the top and cut another. Fit one hole with 
a cork carrying a short glass elbow and connected by 
rubber tubing to a supply of gas. Through the other 
hole insert a cork carrying a straight glass tube of 
about of an inch inside diameter and extending 
into the can about 8 inches. If this second cork does 
not fit tightly, seal it in with sealing wax. Then turn 
on the gas and in a moment or two light it at the top 
of the straight tube. When the gas is burning up well, 
remove the cork carrying the elbow and as you do so 
turn off the gas. The flame will continue to burn at 
the top of the straight tube, but it will grow smaller 
and smaller and finally almost disappear (Fig. 28). 



Waiting for the flame to 
2-necked bottle instead of a 


strike down and ignite the explosive mixture, 
can. 


Using a 


209 









Fireworks 


2 I I 


You may think it has gone out, but it hasn’t. It is 
still playing about the mouth of the tube or reaching 
slowly down to the explosive mixture accumulating in¬ 
side the can, for, as the gas escapes and burns, air 
enters through the open vent. Presently the flame 



The set-up for a gas explosion. As the can fills with gas, a match is 
applied to the tube at the left and at the same time the tube at the right is 
withdrawn from the can. 


strikes down igniting this mixture and producing an 
explosion that will satisfy every requirement of a 
Fourth of July celebration. 

This experiment also illustrates the striking back 
of a Bunsen burner or a gas stove and the back-firing 
of an automobile engine. 











212 


The Boys Own Book of Science 

Another Explosion.—Into this same can but with 
the corks removed pour from 5 to 10 c.c. of gasoline 
or ether. Keep both away from the flame. Wait 
about 2 minutes and then with a long taper bring a 
flame over one of the openings. The explosion will 
be all that you desire. In lighting this explosive mix¬ 
ture never put your face over the can. 

Nitrogen Iodide.—Now I am going to tell you how 
to prepare an explosive substance that will afford you 
no end of amusement. But you must be careful and do 
exactly what I tell you to do. From the drug store 
obtain a few grams of iodine crystals—not tincture 
of iodine. In a test tube place 4 or 5 c.c. of alcohol 
(denatured will serve) and add a considerable quan¬ 
tity of the powdered iodine. Shake this so as to ob¬ 
tain a very strong solution. Mix with it an equal 
volume of the strongest ammonia water. Shake the 
mixture. A black precipitate of nitrogen iodide im¬ 
mediately separates. Pour this onto a filter paper 
placed in your funnel taking pains to get out all of 
the solid. If any remains in the test tube pour the 
filtrate back into the tube and, after shaking, quickly 
pour it onto the filter. 

Now this substance is not at all explosive when 
wet and it will take about an hour for it to dry, possibly 
longer. Remove the filter paper, tear it into several 
pieces, and distribute them in a number of out-of-the- 
way places. Then do not again touch them with your 
hands or go near to them. After about an hour tickle 
one of the pieces with a feather attached to a rod 3 or 


Fireworks 


213 


4 feet long. Even this slight friction will cause the 
nitrogen iodide to explode. And the noise will be ap¬ 
propriate to the occasion. A jar like the stamping of 
a foot will cause it to explode. Blow upon another 
portion of the stuff through a long glass tube, and the 
pent-up energy will be released. If another portion 
has been left in the sun or in a warm place it will 
explode spontaneously upon the slightest provoca¬ 
tion. 

A chemistry “prof” of my acquaintance left some of 
this treacherous stuff in various places about his lecture 
room to dry one night. During the evening the janitor 
entered the room, and, as he shut the door, a sharp ex¬ 
plosion startled him nearly out of his wits. Then, as 
he began hurriedly to walk through the room, explosion 
after explosion greeted his progress. Alarmed and 
terrified, he made his exit and, doubtless to this day, 
congratulates himself upon his narrow escape. 

Wet nitrogen iodide cannot explode, and, after set¬ 
ting it to dry, simply keep at the proper distance. 
When the psychological moment arrives, it will know 
perfectly well how to behave. 

In the foregoing experiments I have given you plenty 
of ammunition for an old-fashioned Fourth of July 
celebration. There are other experiments of this sort, 
but many of them are dangerous unless carried out with 
the utmost care. 


Chapter 24 

SIR HENRY BESSEMER 

A s a lad Sir Henry Bessemer, who later discovered 
the quick process of blowing molten pig iron into 
liquid steel, displayed a wonderful genius for the use 
of tools and the work of invention. Before he was 
out of his teens, he had devised a method for stamping 
deeds, a machine for figuring velvet, and a type-casting 
device. Then one day he had occasion to buy some 
bronze powder and to his amazement found that it cost 
a fabulous price. Why should it cost so much, he 
asked? If he could discover the secret of its prepara¬ 
tion he felt that he could make his fortune. Imme¬ 
diately he set to work. He designed a machine for 
turning bronze into what seemed to him a powder of 
the utmost fineness. But still it was not fine enough. 
Baffled, he abandoned the project for a time. Then 
someone suggested that he examine his powder with 
the microscope. He did so and at once the difficulty 
was revealed. The particles of his powder were little 
curled-up shavings. This gave him his clew and he 
quickly designed a machine which accomplished his pur¬ 
pose. But he never patented it, fearing that someone 
would steal his process. Under the supervision of 

men sworn to secrecy, Bessemer manufactured the 

214 


215 


Sir Henry Bessemer 

powder and sold it at a huge profit. For years this 
source of revenue supplied him with all the funds he 
needed for his work of experimentation and invention. 

And to invent was as natural to Bessemer as it was 
to breathe. In a short time he turned his attention to 
the making of guns and devising improvements in their 
designs. This work required steel, and Bessemer soon 
became convinced that a cheaper and quicker process 
of producing this vastly important raw material was 
imperative. With him always the realization of an in¬ 
dustrial need was a summons to meet it. Long he 
pondered the problem. Then one day a happy thought 
came to him. Why not burn the impurities out of 
molten pig iron and convert it into steel with a blast of 
air blown through the iron placed in an egg-shaped 
crucible. He tried the plan on a small scale in his 
laboratory and it worked. On a bigger scale, it was at 
first a failure, and Bessemer became the laughing stock 
of England. But the old proverb is right, “He who 
laughs last laughs best.” Bessemer perfected his proc¬ 
ess and he was soon manufacturing steel in his own 
works at Sheffield and putting it upon the market at 
$100 a ton cheaper than his competitors could produce 
it. That was an argument that could not be met, and 
the very men who had ridiculed him were soon paying 
him a fortune in royalties for the use of his process. 

For his services as an inventor Bessemer was 
knighted. His remarkable success in everything he 
undertook grew out of his boyhood ambition to 
experiment. 


Chapter 25 


THE CHEMISTRY OF THE ELECTRIC 

CURRENT 

T O the amateur there is probably no more fasci¬ 
nating branch of science work than that of elec¬ 
tricity. There is a magic about this word that always 
appeals to boys. One of the first things that my 
General Science boys want to do is to electroplate 
something. And I presume you are no different than 
they. Let us see what can be done. 

Source of Current.—The first all-important matter 
to consider is where you will get the supply of current, 
or “juice,” as the boys say. If you have in your house 
direct current and have made the lampboard rheostat 
that I described in the chapter on electric furnaces, the 
problem is easily solved. Simply run an extension coil 
from a lamp socket to the lampboard and connect 
through that with your apparatus. For much of this 
work you will not need an elaborate lampboard. Just 
mount 2 or 3 lamps in parallel (in the same manner as 
the lamps on the board diagramed in a previous 
chapter) and turn on one or all, as you may need. A 
single lamp will frequently be sufficient. 

You who are not so fortunate as to have current in 

216 


The Chemistry of the Electric Current 217 

the house or who have alternating instead of direct 
must make cells and batteries. But you can do 
that. 

The bichromate cell will be best for work in which 
you will need much voltage or considerable current. A 
half dozen of these coupled in series will meet most of 
your needs, aside from those of electric furnaces. To 
make such a cell obtain a quart fruit jar and place in 
it 80 g. of chromic acid. Pour onto this 710 c. c. of 
water. Stir the mixture until the acid is thoroughly 
dissolved. Then add slowly and with constant stirring 
45 c. c. of concentrated sulfuric acid. Now to obtain 
electricity by chemical action you must insert in this 
solution a rod of zinc and a rod of carbon. A broad 
flat bar of zinc about a quarter of an inch thick will be 
best for the negative electrode. Solder to it a copper 
wire for connections. For the positive electrode a 
large-size electric light carbon will serve, or better 
the carbon rod from an old dry cell. By means of a 
wooden clamp holder, which you can devise yourself, 
support these in the jar. Do not let them touch and 
see that they dip into the solution as far as possible. 
If you have used the carbon from a dry cell, it will 
have a binding post. If not, you may twist about the 
top of it with pliers a stout copper wire. When not in 
use remove the zinc from the solution. 

To connect these cells in series join the carbon of 
one to the zinc of the next with short lengths of copper 
wire. That will leave a carbon of one end cell to be 
connected through your apparatus with the zinc of the 


21 8 The Boys’ Own Book of Science 

other end cell. A half dozen of these cells will give 
you 12 volts. 

The gravity cell is best adapted to electrotyping 
and electroplating. For such work you do not need a 
large current but a constant one and a cell that can be 
used on closed circuit. To make this cell obtain a half 
gallon battery jar. Suspend in it a large square of 



Gravity cell at the left, and electrodes and holder for bichromate cell at 
the right. 


sheet copper letting the lower edge rest upon the 
bottom and the upper edge extend about half-way up 
the jar. Over the edge of the jar suspend a heavy 
bar of zinc bent hook-shape at one end to catch on the 
edge of the jar and extending horizontally inside the 
jar. To both of these solder copper lead wires. 
(Fig. 29.) 

Into the bottom of the jar throw a handful of blue 



































































The Chemistry of the Electric Current 219 

vitriol and fill it with water containing a few cubic centi¬ 
meters of sulfuric acid. Then place the cell on closed 
circuit. It should never be left on open circuit. The 
blue vitriol will gradually be used up and more must 
be added from time to time. The zinc also must occa¬ 
sionally be replaced. 

Dry cells will serve many purposes, but they are not 
adapted to closed circuit work, such as electroplating. 
This is because they polarize rapidly and the current 
becomes very small. Where you need a large current 
for a short time, six good dry cells will be just the 
thing. 

A rod of carbon and a rod of zinc placed in a jar 
containing a strong solution of sal ammoniac will give 
you a cell similar in principle to a dry cell and suitable 
for many purposes. 

Electrolysis Apparatus.—If you are to carry out 
the electrolysis of water and solutions, some form of 
electrolysis apparatus will be required. It will be 
practically as cheap and much more satisfactory to buy 
a simple form of such apparatus from some supply 
company than to attempt to make one yourself. To 
make one will require platinum foil, and that is quite 
expensive. 

For the boy who wishes to do so, though, I am going 
to describe the construction of a simple form. Obtain 
two small strips of thin platinum foil. They need not 
be more than a quarter of an inch wide and three- 
quarters of an inch long. Pierce each with a small 
hole and attach to it a stout length of copper wire well 


220 


The Boys' Own Book of Science 

insulated with heavy rubber. Bend both ends hook- 
shape and suspend the two electrodes in a small battery 
jar containing water to which has been added a little 
sulfuric acid. Fill two test tubes with the same solu- 



Figure 30. 

Electrolysis apparatus. 


tion and placing a thumb over the mouth of each invert 
them in the jar. Slip their mouths over the platinum 
electrodes and secure them in position by clamps at¬ 
tached to your ring-stand. (Fig. 30.) 

If you have direct current, connect the lead wires of 
the electrolysis apparatus with one lamp of the rheo- 















































The Chemistry of the Electric Current 221 

stat. If you depend upon cells, connect a half dozen 
bichromate cells directly with the apparatus. In either 
case you will immediately obtain action. Bubbles of 
gas will rise from each electrode and collect in the test 
tubes. Y ou will note that the gas accumulates twice as 
fast in one as in the other. This is from the negative 
pole, or cathode. The other electrode is called the 
anode. 

When the cathode tube is about two-thirds full, 
break the circuit. Loosen the clamp and placing your 
thumb beneath the mouth of the test tube containing 
the smaller quantity of gas quickly invert it and thrust 
into it a glowing splint. The brilliancy with which the 
gas supports combustion proves it to be oxygen. 
Simply lift the other tube from the water and present 
it to the flame. The explosion which you get together 
with the mist which collects on the walls of the tube 
shows this gas to be hydrogen. 

The other type of apparatus, which you can ob¬ 
tain from a supply house, is simpler and requires 
a smaller quantity of solution. If you use it, the 
openings at the tops of the tubes will need to be closed 
with short pieces of rubber tubing and pinch clamps. 
To use this apparatus open the pinch clamps and fill 
the tubes to the top with the solution. Then connect 
the electrodes with the source of current. Close the 
pinch clamps and allow the gas to collect. In testing 
for oxygen, hold over the tube a glowing splint and 
slowly open the clamp. The splint will be kindled into 
a flame. To obtain the hydrogen test, hold an in- 


222 


The Boys Own Book of Science 

verted test tube over the other tube and open the 
clamp. Being lighter than air the hydrogen will rise 
and fill the tube. Hold the tube of gas to the flame 
and it will burn with a sharp explosion. 

Testing Electrolytes and Non-Electrolytes.—Some 
substances in solution will conduct the electric current 
and others will not. Those which do are called elec¬ 
trolytes and those which do not are called non-electro¬ 
lytes. It will afford you an interesting piece of real 
research to test out with your apparatus the electrical 
conductivity of a number of compounds, some organic 
and some inorganic. Since chlorine attacks platinum, 
it will be impossible for you to use the solution of a 
chloride, as common table salt for instance. 

First rinse out the apparatus thoroughly and do 
so again after each trial. Then try the action of the 
current on distilled water. Is there any action? Is 
distilled water a conductor? To determine this ob¬ 
serve whether any bubbles appear at either electrode. 
If they do, the substance is an electrolyte. The bubbles 
may be very small and very few. If so, the substance 
is a very poor conductor. If you are using a i io-volt 
source of direct current and a lamp for resistance, the 
lamp will light, if the solution is a good conductor. I 
think you will find that distilled water is a non¬ 
conductor. 

Next try tap water. You will probably get a slight 
action in this case, because tap water always contains 
some mineral matter in solution. The extent to which 
it conducts the current is an indication of the quantity 


The Chemistry of the Electric Current 223 

of mineral matter it contains. You have already seen 
that water containing sulfuric acid is an electrolyte. 
In order that water may conduct the current, it is nec¬ 
essary that it have some substance in solution, and the 
compound in solution is really the electrolyte. But 
not all compounds will make water a conductor. 

Now place in your apparatus a quite strong solution 
of sodium sulfate which you have colored with blue 
litmus. Pass the current for a few minutes and you 
will note that the solution about the cathode becomes a 
deeper blue, while that about the anode changes to red. 
You will remember that an acid turns blue litmus red, 
while a base gives the reverse change. Chemical 
changes are being produced with the formation of an 
acid at one pole and a base at the other. Electrolysis 
is the name given to the chemical changes which occur 
when a current is passed through the solution of an 
electrolyte. 

Test the conductivity of alcohol and of a solution of 
sugar. You will be unable to detect any action. These 
are organic, or carbon, compounds, and most organic 
substances are non-electrolytes. That is one of their 
chief distinctions from mineral compounds. 

The strength of an acid or base may be determined 
by its ability to conduct the electric current. Dissolve 
4 g. of sodium hydroxide and 5.6 g. of potassium hy¬ 
droxide in separate beakers, each containing 100 c.c. of 
water. Test the conductivity of each solution sepa¬ 
rately, rinsing the apparatus thoroughly after each test. 
Which seems to be the better conductor and the strong- 


224 The Boys Own Book of Science 

er base? Test also the conductivity of ammonia water 
and limewater. Can you understand now why am¬ 
monia water may be applied directly to the clothing in 
the removal of stains, and why limewater may be used 
as an eye wash and even taken internally? 

Place some vinegar in your apparatus and pass the 
current. How does its conductivity compare with that 
of sulfuric acid? Do you understand why vinegar is« 
used on our food? Prepare a saturated solution of 
carbon dioxide by passing the gas through water for 
some time. Then determine whether its solution is an 
electrolyte. Why can you drink without injury such 
“vast” quantities of soda water? 

Electroplating.—Now we are coming to what you 
have been waiting for. To have been able to electro¬ 
plate another substance with a bright shiny metal 
would have intoxicated the alchemist with joy. But 
the electric current was unknown in his day. 

Place 250 g. of blue vitriol (copper sulfate) in a bat¬ 
tery jar and cover it with a liter of water (1000 c. c.). 
Stir it well and allow the mixture to stand overnight. 
7 'hrust into the solution a carbon rod from an old dry 
cell and a strip of copper having about the same square 
surface as that of the carbon rod. Using either two 
bichromate cells or two dry cells grouped in series, 
that is, the positive pole of one joined to the negative 
pole of the other, connect them with copper wire to 
the electrodes of the electroplating bath. Connect the 
positive pole, or the carbon, of the battery to the 
copper strip and the negative pole, or zinc, of the 



Electroplating with current from gravity cell at the left. Testing electrolytes at 
the right. Lighted lamp in series with apparatus shows that the solution is an 
electrolyte. 


225 














The Chemistry of the Electric Current 227 

battery to the carbon rod. Allow the current to pass 
for 5 minutes and then examine the carbon rod. Note 
the deposit of bright copper. Also examine the copper 
strip. Does it look any different than before you 
passed the current? 

Now reverse the connections between the battery 
and the electrodes of the bath. Pass the current again 
for 5 minutes. Then examine the carbon rod. Is it 
still bright? What h as happened to the copper de¬ 
posit which you observed before? Examine the copper 
strip. Does it look any brighter? Do you not see 
that copper is driven out of solution by the current and 
deposited upon the negative pole of the bath, and that 
at the same time copper is dissolved from the positive 
pole of the bath? For these reasons we place the ob¬ 
ject to be plated at the negative pole, or cathode, and 
make the positive pole, or anode, of copper. In this 
way the strength of the solution is kept the same, but 
the copper anode is gradually used up. 

If you use direct current and a lamp board rheostat, 
the process is exactly the same. But you will have to 
determine which wire is positive and which negative. 
To do so turn on the current and dip the ends of the 
copper lead wires into the copper sulfate solution for a 
few moments. The one upon which you obtain a 
copper deposit is the negative. For this work use a 
single lamp. 

To do a good piece of electroplating work a battery 
consisting of two gravity cells grouped in series will be 
best. It will give a small but steady deposit, and that 


228 The Boys’ Own Book of Science 

is what you need for a fine even coating. Clean a nail 
or an old knife blade thoroughly with fine sandpaper. 
Scour it until it is bright. Hang it at the cathode of 
the electroplating bath, that is, you will connect to it 
the zinc pole of the battery. For the anode use a strip 
of copper as before. Allow the current to run a con¬ 
siderable time. You can tell when to break the circuit 
by the amount of the deposit. You should obtain a 
deposit of good quality. Whenever the deposit is 
dark and spongy and does not stick well to the surface, 
you are using too much current and the surface was 
probably not well cleaned. The current will not be too 
large with gravity cells. When you use direct current 
without proper resistance, it will be. 

Making an Electrotype.—An electrotype is a cop¬ 
per plate from which a page of a book is printed or 
some “half-tone” or “line-cut” is reproduced. Phono¬ 
graph records are also stamped from electrotypes. 

It will be interesting to make an electrotype. In a 
small shallow basin melt lumps of beeswax, making a 
layer at least an eighth of an inch thick. When the wax 
has hardened, rub it over thoroughly with finely pow¬ 
dered graphite. Then select some object you wish to 
electrotype. It may be any metallic souvenir having a 
fairly smooth surface with or without inscription. But 
never attempt to copy a coin. That is illegal. Dust 
the object with graphite and press it firmly into the wax 
until a deep clean-cut impression is made. With a 
knife cut out and remove the square of wax containing 
this impression. Now dust the wax again being sure 


The Chemistry of the Electric Current 229 

that the graphite is worked into all of the lines and 
grooves. Rub it to a smooth shiny surface. Finally 
attach a copper wire to the upper side of the wax form 
and suspend it at the cathode of the copper plating 
bath. At the anode, as before, suspend a strip of cop¬ 
per of the same area as that of the wax. Connect the 
bath with two gravity cells and allow the current to 
run for a considerable period. Probably 24 hours will 
not be too long, but the time will depend upon the thick¬ 
ness of the layer of copper that is deposited. 

To make the electrotype permanent it will require 
backing with melted tin. When the required thickness 
of copper has been obtained, remove the form from the 
bath and carefully pry the electrotype loose with a 
knife blade. With molding clay make a shallow form 
of the exact shape of the electrotype. Have the bot¬ 
tom perfectly smooth and level. Place the electrotype 
face down in this form being careful to make the edges 
fit close up to the sides. Put this form in an oven and 
let it come up to as high a temperature as possible. 
Melt a quantity of tin in an iron dish and holding the 
dish with tongs pour the molten metal into the form. 
Then let the oven and contents cool. Remove the 
electrotype, ink it, and take off a copy on white paper. 

Alundum cement or fire clay and water glass will be 
excellent material for making the form. 

Silver Plating.—If you wish to silver plate, the 
process is exactly the same as that of copper plating. 
In a small battery jar place a dilute solution of silver 
nitrate. If you have prepared silver nitrate crystal^ 


230 The Boys’ Own Book of Science 

as directed in the chapter on metals, they will be suit¬ 
able for use here. One gram to 100 c. c. of water will 
be sufficient. For an anode this time you will need a 
silver piece. Attach a wire to it and suspend it as you 
did the copper strip. The object which you plate must 
be perfectly clean. Scour it with sapolio and fine sand 
and rinse in clean water. Use gravity cells, as before, 
and allow the current to flow for some time. 

The Storage Cell.—One of the most important 
chemical effects of the electric current is to be found in 
the storage cell. You of course know that this cell 
does not store up electricity, but simply converts elec¬ 
trical energy into chemical energy, which may be 
changed back again into electricity at our convenience. 

To make a simple storage cell place in a tumbler a 
dilute solution of sulfuric acid, made by pouring 25 c. c. 
of the concentrated acid into 200 c. c. of water. Sand¬ 
paper two strips of heavy sheet lead and suspend them 
in the solution. Connect these with a source of cur¬ 
rent. If you have direct current, connect in series with 
the cell 2 lamps in parallel. If you depend on cells, 
use either 2 bichromate cells or 3 dry cells. Let the 
current pass for 5 minutes. Then disconnect the 
charging battery and try the action of the storage cell 
on an electric bell. Does it ring? You will find that 
the action soon ceases. Charge it again, and, as you 
do so, note that bubbles of gas rise around each of the 
lead strips. At the anode oxygen escapes and at the 
cathode hydrogen. Remove each strip. You will 
find the anode covered with a chocolate colored deposit 


The Chemistry of the Electric Current 231 

of lead peroxide. This is a new chemical compound 
which has been formed by the action of the electric 
current. I he cathode you will observe remains un¬ 
changed. When the battery is disconnected and the 
cell is placed on closed circuit a reverse set of chemical 
changes occurs, which sends a current in the opposite 
direction to the charging current. 

You may wish to make a real storage cell. If you 
do, obtain from a local electrical store a regulation 
container and two lead grids. Make a stiff paste by 
mixing the lead oxide known as litharge together with 
dilute sulfuric acid and glycerin. With a small wooden 
paddle press this paste into the perforations of the lead 
grids. Insulate these two grids from each other at 
top and bottom with pieces of heavy rubber tubing 
and bind the two together with strong rubber bands. 
Prepare a solution of sulfuric acid of the same strength 
as that used in the simple cell. Fill the container 
nearly full of this solution and set into it the two grids. 
To each grid attach a copper wire and connect the 
cell to a source of current. If the cell is to be well 
charged, the current must run for a number of hours. 
Of course it would not be profitable from a practical 
standpoint to charge storage cells from an ordinary 
battery. But if you make a number of these cells and 
connect them together in series, you will be able to 
charge them from your direct current lighting circuit, 
using the lampboard rheostat to get the proper amount 
of current. Or you may have them charged at a bat- 
tery service station. I think, however, that you will 


232 The Boys' Own Book of Science 

be able to meet your electrical requirements without 
home-made storage cells. But it will be a simple 
matter for you to charge your own and the radio bat¬ 
teries of your friends by means of your rheostat and 
source of direct current. 

The Chemical Action of a Simple Cell.—The sim¬ 
plest cell that you can make consists of strips of copper 
and zinc placed in a dilute solution of sulfuric acid. 
When this cell is on open circuit, examine the copper 
strip and note that there are no bubbles on it. Prob¬ 
ably there will be bubbles about the zinc for reasons 
which we shall presently explain. Now bring together 
the wires from the two plates and watch the copper 
plate again. Almost immediately you will observe a 
myriad of fine bubbles rising in a sheath about the 
plate. These are bubbles of hydrogen gas. On 
closed circuit, the zinc goes into solution driving the 
hydrogen of the acid over to the copper. This hydro¬ 
gen is in the form of little positively charged particles 
called ions. 1 hese ions deliver their positive charges 
to the copper plate and then bubble off as hydrogen 
gas. As the zinc ions from the other plate go into 
solution they carry away with them positive charges, 
therefore leaving the plate itself with a larger quantity 
of negative electricity than positive. We thus see that 
the copper plate comes to be charged positively and the 
zinc plate negatively. 

There are two other characteristics of the electric 
cell which must be mentioned. They are local action 
and polarization. Local action is the solution of the 


The Chemistry of the Electric Current 233 

zinc because of impurities in it. This occurs both on 
open circuit and closed circuit and wastes both the zinc 
and the acid. Each little particle of impurity, usually 
carbon, sets up with a nearby particle of zinc a tiny 
cell, and there are myriads of these cells. To prevent 
this action, you must cover the zinc with mercury or use 
chemically pure zinc. Polarization is the greatly di¬ 
minished current resulting from the accumulation of 
discharged hydrogen bubbles on the positive plate. 
This decreases the voltage of the cell and increases its 
resistance, both of which diminish the current. The 
bichromate and dry cells provide oxidizing agents 
which partly dispose of the hydrogen and eliminate to 
some extent the effects of this action. 

There is a host of chemical industries which depend 
upon the electric current for their success. With elec¬ 
tric energy from Niagara Falls in huge chemical plants 
girding the brow of the great cataract are made 
carborundum, Acheson graphite, calcium carbide, alu¬ 
minum, metallic sodium and potassium, calcium carbide, 
Alundum, caustic soda, chlorine, hydrogen, oxygen, 
calcium cyanimide, and many other products of im¬ 
mense importance. The vision of Sir Humphry Davy, 
who first applied the electric current to the solution of 
chemical problems, has come to a tremendous 
realization. 

One of the most interesting applications of the elec¬ 
tric current occurs in the refining of copper, silver, gold, 
and platinum. Considerable quantities of the silver, 
gold, and platinum which we use are electrically sepa- 


234 The Boys’ Own Book of Science 

rated as “impurities” in connection with the metallurgy 
of copper and lead. To go through the refining de¬ 
partments of one of these large smelters and see the 
separation of the precious metals in quantities that 
would make you richer than Croesus is a most interest¬ 
ing experience. But we cannot describe these proc¬ 
esses here. We must hurry on to other subjects 
equally as important to the home-laboratory worker 
as any that have preceded. 


Chapter 26 


SIR WILLIAM PERKIN 

H ad anyone wandered into the home laboratory 
of Sir William Perkin—then just plain Bill Per¬ 
kin—during the Easter vacation of 1856 he would 
have observed this lad hard at work over a dirty black 
mess of coal tar. He was endeavoring to extract the 
drug quinine from this mixture of carbon compounds, 
a problem which had been assigned him by his profes¬ 
sor of chemistry at the Royal College of Science in 
London. One evening just at the close of a disappoint¬ 
ing day’s work, young Perkin poured alcohol into a 
mixture of aniline oil and other chemicals with which 
he had been working. To his amazement and delight, 
there flashed into view a beautiful purple dyestuff. 
The color fascinated him. He wondered what should 
have caused it. He resolved immediately to separate 
this compound and to discover the method of its prepa¬ 
ration. For days he worked upon the problem, and, 
although it baffled him for a time, he would not give up. 
At length he discovered the secret and the result was 
mauve, the first of the aniline colors. 

Here was Perkin, still a freshman in college and only 
eighteen years old, making one of the greatest discov¬ 
eries in the history of chemistry. So enthusiastic did 

235 


236 The Boys’ Own Book of Science 

he become that he decided to leave college and begin 
the manufacture of the new dyestuff. His father as¬ 
sisted him financially, but where was the machinery for 
carrying out his process? It did not exist. Perkin, 
not yet out of his teens, was compelled to design it and 
supervise its manufacture. To add to his difficulties 
the aniline oil necessary for his purpose was not to be 
had. He must prepare it from benzene. And again 
strong nitric acid could not be bought on the market. 
He had to distil it from Chili saltpeter and sulfuric 
acid. But Perkin solved every problem and had soon 
founded a vast new industry. He discovered other 
coal tar dyes and his business grew until he became a 
wealthy man. And then what did Perkin do? He 
abandoned chemical manufacture and built himself a 
private laboratory where he might spend the rest of his 
years in the delightful work of original research. And 
working there quietly in his laboratory year after year, 
Perkin added vastly to our knowledge of organic chem¬ 
istry. So distinguished did he become that his king 
knighted him and he was honored by the leading scien¬ 
tific societies of every land. 


Chapter 27 

THE CHEMISTRY OF LIGHT 


W hile I was in college I served for three years 
as laboratory assistant in chemistry. One day 
I was assisting my professor with some experiments in¬ 
volving the chemical effects of light. In a small flask 
we prepared a mixture of equal volumes of hydrogen 
and chlorine gases. We sealed this tightly and placed 
it under a very heavy battery jar, one whose sides were 
fully a quarter of an inch thick. In front of this we 
ignited a heap of flash powder. There was a sharp 
explosion. We repeated the experiment a number of 
times. It seemed to be perfectly safe and we enjoyed 
the fun. It was equal to a whole Fourth of July 
celebration. Then of a sudden there came an explo¬ 
sion more violent than the others. The big battery 
jar was blown to fragments and the flying glass cut us, 
but not seriously. We were almost dazed. We had 
gotten much more than we bargained for. We might 
have lost our sight or even our lives. We had staged 
altogether too striking a demonstration of the chemical 
effects of light. I have repeated the experiment once 
since, and with similar results, although I took great 
pains to protect myself by placing a heavy glass screen 
between me and the explosive mixture. I consider it 

too dangerous ever to repeat again. 

237 


238 The Boys’ Own Book of Science 

Hydrogen and chlorine have an exceedingly strong 
affinity for each other. Under the influence of heat or 
the chemical rays of light they unite with explosive 
violence. The light from burning magnesium, the 
combustible substance in flash powder, is particularly 
rich in these chemical rays. Other chemical reactions 
are brought about through the energy of light. The 
trees and plants, breathing through their leaves the 
carbon dioxide of the air and absorbing water through 
their roots by means of sunlight, unite them into woody 
fiber, stalk, and flower. In the heat of burning coal 
we are but utilizing the products of the chemical energy 
of the sun’s rays stored up for us in past geologic ages. 
The marvels of modern photography would be impos¬ 
sible without the chemical effects of the violet rays of 
the solar spectrum. 

Blue-printing.—Blue-prints, so essential to modern 
architectural and engineering work, are produced by 
chemical reactions wrought through the agency of sun¬ 
light. If possible, obtain from some blue-printing firm 
a yard of blue-print paper. Cut out a small square, 
lay upon it a key or some other opaque object, and ex¬ 
pose it to the sun's rays for about a minute. You will 
note that the green color of the paper begins to turn 
blue. Then place it in water and a deep blue will 
appear wherever the sunlight has fallen, but the part 
covered by the object will become white. The washing 
at once develops and fixes the print. The water 
completes the chemical changes started by the sunlight 
and at the same time dissolves out the unaffected salts 


The Chemistry of Light 239 

in the portion of the paper covered by the object. 
When the print is dry it will be permanent. It will not 
disappear under the influence of sunlight. Even such 
an accomplishment as this would have been hailed with 
joy by the pioneers in the quest for the secrets of 
photography. 

With india ink make a drawing or sketch some de¬ 
sign on the oiled paper used by draftsmen. Place this 
over a square of blue-print paper and repeat the above 
process. 

To understand the chemistry of blue-printing , it 
will be necessary for you to do some preliminary experi¬ 
ments with iron salts. Prepare rather dilute solutions 
of ferric and ferrous salts. Chlorides, sulfates, or ni¬ 
trates will be satisfactory. You will also need solu¬ 
tions of potassium ferricyanide indicator and the 
reducing agent oxalic acid. 

Fill a test tube half full of water and add a few 
drops of the ferrous solution. Follow this with a few 
drops of potassium ferricyanide indicator. You will 
obtain a deep blue color. This is a test for a ferrous 
salt. Now repeat the experiment, but substitute the 
ferric solution for the ferrous. This time you will ob¬ 
tain an olive green, varying in shade according to the 
amount of ferric salt present. 

Now fill a test tube one-sixth full of ferric solution. 
Add an equal quantity of oxalic acid (it should be a 
saturated solution), dilute the contents of the tube well 
with water, and add a few drops of potassium ferri¬ 
cyanide. Expose this tube to the direct rays of the 


240 


The Boys’ Own Book of Science 

sun. Very soon you will observe streaks of blue ap¬ 
pearing in the tube, and gradually the whole solution 
will change color. If the color is not a good blue but 
of a greenish cast, you have used too much of the ferric 
salt. You may have to experiment some to get the 
right proportions. 

What has happened? The color of the solution 
was first green, owing to the presence of the ferric salt. 
Ferricyanide gives a blue only with a ferrous salt. 
Therefore, if a blue color appears, it must be that the 
ferric salt has been changed, or reduced, as we say, to 
ferrous form. And that is just exactly what has hap¬ 
pened. The chemical rays of the sun have produced 
this change, but let us examine this further. We used 
oxalic acid. Did that have anything to do with the 
chemical reaction? To discover the answer, prepare 
another test tube exactly as before, but leave out the 
oxalic acid. Expose it to the sunlight. You will find 
that no color change occurs. Evidently the chemical 
rays of the light are powerless without the assistance 
of the acid. The oxalic acid acts as a medium to bring 
about the change. We have still to learn whether the 
color change might not be produced without the aid of 
the sunlight. Prepare a test tube exactly as you did 
the first one, using ferric salt, oxalic acid, and indicator, 
but this time place it in the dark. After a half hour 
examine the mixture. No change occurs. Therefore 
we see that the blue-print reaction consists in the reduc¬ 
tion of a ferric salt to ferrous form through the 
agencies of a reducing agent and sunlight. 


241 


The Chemistry of Light 

Preparation of Blue-print Paper.—If you wish to 
prepare blue-print paper, two solutions will be required. 
The substances and their proportions are given below. 

Solution I: 

Ferric ammonium citrate, 40 g. 

Water, 200 c.c. 

Add ammonia water until a decided color change 
occurs. 

Solution II: 

Potassium ferricyanide, 40 g. 

Water, 200 c.c. 

Prepare a mixture of equal parts of the two solutions 
and for every 100 c.c. of the mixture add 30 c.c. of a 
saturated solution of oxalic acid. The mixture must 
be kept in the dark. 

Obtain a good quality of unglazed paper and draw 
squares of it across the surface of the mixture, dis¬ 
tributing the liquid as evenly as possible, but keeping 
the upper side dry. Let these squares dry in the dark. 
Press them, if you like, between two smooth surfaces 
of wood upon which you have placed a heavy weight. 
Like all blue-print paper, they will have a greenish 
color before exposure to the light. The process of 
making a print is exactly similar to that with the regu¬ 
lation paper already described. 

Silver Salts in Photography.—The problem of 
causing the rays of the sun to paint our pictures was a 
most baffling one. The Frenchman Daguerre solved 
it. He had exposed in his very crude camera of that 



242 The Boys 1 Own Book of Science 

day a silver plate covered with a thin film of silver 
iodide, prepared by exposing the plate to the vapor of 
iodine. The chemical rays of the sun produced an 
imprint of the object focused upon it, but he could find 
no means of developing the image. He worked upon 
the problem for years without success. Then one eve¬ 
ning, while he was engaged upon this fascinating quest, 
he was unexpectedly called from his laboratory. 
Quickly he thrust into a cupboard the silver plate upon 
which he was working. Imagine his delight, when the 
following morning he opened the cupboard and found 
a beautiful picture. During the night in some mysteri¬ 
ous way the image had been developed. But how? That 
was a question which he must answer. His first step 
was to expose another plate in his camera and leave it 
in the cupboard the following night. Again the picture 
was developed. Then he began his search. He tested 
every chemical in the cupboard. At last he discovered 
that the plate had been placed near to a dish of mer¬ 
cury and that the vapor of this liquid metal had 
brought out the image. He quickly perfected the 
process and in a short time was making the first real 
photographs ever produced. 

To learn the chemical effects of light on silver salts 
and the reactions which take place in the developing 
and fixing of a plate, film, or print, you will need four 
solutions: 

36 g. of potassium bromide per liter of distilled 
water. 

17 g. of silver nitrate per liter of water. 


The Chemistry of Light 243 

250 g. of u hypo” (sodium thiosulfate) per liter of 
water. 

10 g. of hydrochinone, 20 g. of sodium sulfite, 1 g. 
of potassium bromide, 1 g. of citric acid, 20 g. of 
sodium carbonate to 1600 c.c. of water. 

This last solution is the developer. 

The silver nitrate and developer should be kept in 
dark colored bottles or away from the light. Since 
these volumes will be larger than you will require, you 
may prepare only one-tenth of the quantities indicated. 

Fill a test tube one-fourth full of water and wrap it 
in heavy dark paper. Black is best. From burettes 
or a small measuring cylinder add 1 c. c. each of silver 
nitrate and potassium bromide solutions. This will 
precipitate silver bromide, one of the most sensitive 
salts to the effects of sunlight. Gently shake the tube 
to mix the precipitate with the liquid and removing 
the paper expose it to the action of the direct rays of 
the sun for 2 minutes. There may be some discolora¬ 
tion. This is due to the presence of organic water. 

Pour into the test tube 5 c.c. of developer and con¬ 
tinue to expose to the sunlight for 3 minutes. You 
will note that the contents of the tube rapidly turns 
dark. Add 10 c.c. of hypo and with your thumb over 
the mouth of the test tube invert it several times to 
insure mixing. The contents of the tube begins to 
clear and black particles appear. The sunlight and 
developer reduced some of the silver bromide to metal¬ 
lic form and the hypo has dissolved the unaffected 
silver salt. The black particles are metallic silver. 


244 The Boys’ Own Book of Science 

To prove this pour the liquid through a filter paper in 
your funnel and wash the black residue by passing re¬ 
peated small portions of water through the filter. 
Place the portion of the filter paper containing the 
black residue in a test tube and add dilute nitric acid. 
The black particles will dissolve. Filter the solution 
into a clean test tube and wash it through with a little 
water. Add to the filtrate a few drops of hydrochloric 
acid and you will obtain a white precipitate, which will 
dissolve in ammonia water. This is the test for silver. 

In a similar way prepare another test tube of silver 
bromide but this time keep it well wrapped in black 
paper. Add the developer as before and allow it to 
stand unexposed to the light for a few minutes. Then 
add io c.c. of hypo and remove the wrapping. You 
now see no black particles. The developer alone 
without the aid of sunlight is unable to reduce the 
silver bromide. 

When a plate or film is exposed in the camera to the 
action of the light a chemical change is started which 
the developer is able to take up and continue. This 
action is greatest on those portions of the plate which 
have received the most light. Thus the light portions 
of the object, which reflect the most rays into the 
camera, will appear dark on the plate, while the dark 
portions will appear light. In this way we get a 
“negative.” Yet, as you see, when the picture has 
been developed, there is still a considerable quantity of 
unchanged silver bromide. This must be removed or 
when taken into the light the picture will darken and 


24 5 


The Chemistry of Light 

disappear. Therefore we immerse the developed 
plate in hypo which dissolves the unaffected silver 
bromide. After washing and drying, the plate is ready 
for use. As many of you know, the process of making 
a print is exactly the same as the one just described. 
But now we reverse the lights and shades and there¬ 
fore obtain a positive. 

Making a Photograph without a Camera.—This 
stunt is not as difficult as you might at first think. To 
carry it out you will need what is called “self-toning” 
paper. Such prepared paper already contains a de¬ 
veloper and needs only “fixing” with hypo, washing, 
and drying. You can easily obtain this paper from 
any dealer in photographic supplies. Expose a small 
square of it to the sunlight. It will quickly turn to a 
deep brown except the portion protected from the light 
by your thumb or finger. 

From some book select a picture which you wish to 
reproduce. The reverse side should be plain, and the 
paper should be thin enough so that, when you hold it 
to the light with the plain side toward you, the picture 
may be clearly seen. Under the picture place a piece 
of self-toning paper with the glossy side up. Cover 
the two with a glass plate and expose them to the sun¬ 
light for a few minutes. The time will vary from 5 
to 10 minutes according to the thickness of the paper 
and the brightness of the light. Remove the paper 
and immerse it in a solution of hypo for 10 minutes. 
Then wash the print by placing it in a large basin of 
clean water for about 20 minutes and dry it. 


246 The Boys’ Own Book of Science 

To obtain a positive, place this negative face down 
on another piece of self-toning paper and expose to the 
sunlight again. Follow this by fixing, washing, and 
drying, and you will obtain a print that will surprise 
and delight you. 

Action of Light on a Copper Compound.—Prepare 
a strong solution of cupric chloride. Immerse in it a 
sheet of polished copper. This treatment will pre¬ 
cipitate on the copper a film of white cuprous chloride. 
Wash the plate in running water. Then place over it 
some design cut from heavy paper and expose to sun¬ 
light. The uncovered portion will be darkened by the 
sun’s rays, while the protected portion will remain 
white. 

Sunlight is a Powerful Antiseptic.—Direct sunlight 
will kill the germs of tuberculosis, diphtheria, and 
typhoid in from 6 to 8 hours. 


Chapter 28 


THOMAS A. EDISON 

N ewsboy and “candy butcher” on the Grand 
Trunk Railway at fourteen, most expert teleg¬ 
rapher in the Western Union System at twenty-two, 
world-renowned inventor before he was thirty, and 
one of our foremost scientists ever since—such has 
been the career of Thomas A. Edison, who as a lad 
spent every spare moment experimenting in a home- 
laboratory. 

So interested was young Edison in performing ex¬ 
periments that he turned the baggage car of his train 
into a laboratory and print-shop. There he published 
a small paper giving the very latest news, which he 
obtained from telegraph operators along the way. At 
one time he sold as many as five hundred copies of each 
issue at three cents a copy. But Edison’s fondness for 
experiments more than once got him into trouble. One 
day while at work in his baggage-car laboratory a 
bottle of phosphorus was jarred to the floor and imme¬ 
diately blazed up setting the interior of the car on fire. 
In the midst of his trouble who should appear but the 
conductor, an irate Scotsman, who had but little sym¬ 
pathy with Edison’s laboratory “whims.” Seizing a 
pail of water he dashed out the fire and then at the 

24 7 


248 The Boys’ Own Book of Science 

first station stopped the train and pitched Edison off, 
laboratory, print-shop and all. 

About this time Edison snatched the three-year-old 
son of one of the Grand Trunk telegraph operators 
from in front of an approaching express train, nar¬ 
rowly escaping with his own life. To reward him the 
father taught Edison telegraphy. Although he was 
then but seventeen, Edison applied for and received 
the position as night operator in his home town. His 
father allowed him to have a laboratory on the third 
floor of the house and in it he persisted in working 
during the daytime instead of sleeping, as he should 
have done. As a result, Edison frequently fell asleep 
at night and was severely censured by the train dis¬ 
patcher. After a while the dispatcher hit upon the 
idea of having Edison send over the line to him the 
signal of the letter “A” every half hour, thinking that 
this would surely keep him awake. It worked beau¬ 
tifully for a few nights. Then Edison saw that he 
must devise some scheme to get more sleep, for he 
would not give up his laboratory. One evening he 
appeared at the station with a queer looking contriv¬ 
ance, which he had constructed in his laboratory during 
the day. With some wire he connected it to the tele¬ 
graph instruments on the desk and the clock on the wall. 
Then he sat down to see what would happen. When 
the half-hour came, right on the dot, the device closed 
the circuit and sent a very good imitation of the letter 
“A” over the wire. He waited another half-hour and, 
satisfied that the mechanism was perfect, went to sleep. 


Thomas A. Edison 


249 


The dispatcher thought he had become a model oper¬ 
ator, until one night when he happened to be at the 
next station down the line. Hearing the signal come 
through as usual on the half-hour, he pulled out the 
switch and called Edison, thinking he would have a 
chat with him. But to his amazement no one an¬ 
swered his repeated calls. After fifteen minutes he 
rushed out of the office and jumping upon a hand-car 
hastened to the rescue. Arrived at the station, he 
peered anxiously in at the window more than half 
expecting to find Edison dead of heart failure or killed 
by bandits. Imagine his surprise to find the “model 
operator” peacefully sleeping on a couch in a corner of 
the office. His first impulse was to give him a rude 
awakening, but spying the curious looking contraption 
on the desk, he sat down to see what would happen. 
The dispatcher did not have long to wait, and although 
he had to admire the ingenuity of the young inventor, 
he was compelled to dismiss him. 

Edison then entered upon the life of a wandering 
telegraph operator, drifting from place to place, and 
gradually becoming the cleverest man in the service. 
At length he found himself in Boston where he re¬ 
mained for a short time and then went to New York, 
arriving penniless. He borrowed money to buy a 
breakfast, and then walked into the operating room of 
a central office for the distribution of stock quotations 
to the brokers of the financial district. He had not 
much more than entered when the main telegraph in¬ 
strument which sent out the reports broke down. 


250 The Boys’ Own Book of Science 

Pandemonium set in. Three hundred boys, one from 
every broker’s office on the street, came rushing in to 
know what the trouble was. The manager of the of¬ 
fice lost his head, and the superintendent was frantic. 
Edison quietly walked over to the instrument, located 
the trouble, and volunteered to fix it. The superin¬ 
tendent excitedly directed him to do so and to be 
“quick.” Deftly Edison removed a broken spring, 
which had fallen between the gear wheels, and set the 
machine in operation. The boys disappeared and 
silence reigned once more. But the superintendent 
called Edison into his office and made him foreman of 
the company at three hundred dollars a month. The 
suddenness of his change of fortune almost took Edi¬ 
son’s breath away, but he resolved to make good. And 
he has been making good ever since. 

Here Edison began his wonderful career as an in¬ 
ventor. He had soon patented a number of improve¬ 
ments on the stock tickers of that day. Then the 
president of the company, General Lefierts, called him 
in and asked how much they were worth. Edison says 
he had intended to ask five thousand dollars and come 
down to three thousand if necessary. But when the 
time came, he did not have the nerve to ask so much 
and so he says, “General, suppose you make me an 
offer.” “How would forty thousand dollars strike 
you?”, General Lefferts replied. Edison says this 
caused him to come as near fainting as he ever did, but 
he managed to say that he thought it was fair. 

He received his money and opened shops in New 


Thomas A. Edison 


251 


Jersey where he has invented systems of duplex and 
quadruplex telegraphy, the phonograph, the incandes¬ 
cent lamp, motors and dynamos, the moving picture 
machine, his famous storage cell, and much more. 

The supreme ambition of Edison’s life was to be¬ 
come an inventor, and it came from his early work in a 
home laboratory. 


Chapter 29 
SPECIAL TESTS 

A nd now we are coming to some real chemical 
analysis. That is what you have been waiting 
for. You want to learn how to analyze something— 
to know how the chemist is able to tell just what sub¬ 
stances are present in some unknown sample. Nothing 
is more fascinating than this kind of work. But it 
calls for the utmost care, keen observation, and sound 
judgment. If your life were to depend upon the testi¬ 
mony of a chemist in a murder trial, you would want 
him to be pretty sure of his facts. Of if you were to 
be prosecuted for selling food containing adulterants 
or illegal preservatives, you would not want the chem¬ 
ist to be doing any guess-work in the matter. 

The Two Common Alcohols.—We have heard a 
great deal about alcohol in the last few years and in 
particular about the frightful effects that result from 
carelessness or ignorance in the use of wood alcohol. 
We can find no better starting point in our work of 
commercial analysis than to learn how to distinguish 
chemically between wood alcohol and grain alcohol. 

Let us begin with a consideration of grain alcohol, 
or ethyl alcohol, as it is known in chemistry. This 

alcohol results from the fermentation of sugar. It 

252 


253 


Special Tests 

has been known from the earliest times, and, although 
its use as a beverage has been quite rightfully pro¬ 
hibited, the industrial uses of alcohol are just as im¬ 
portant as ever. It is used in medicines, drugs, and 
extracts. It is an excellent solvent for organic sub¬ 
stances. It is used in the manufacture of paints and 
varnishes. It is a fuel. By its oxidation we obtain 
acetic acid, and when distilled with bleaching powder 
the product is chloroform. It is the starting point in 
the preparation of ether. And there are many more 
uses. Therefore, you see, that this alcohol is one with 
which you will often meet, and it becomes of impor¬ 
tance to be able to detect its presence with perfect 
certainty. 

To learn the test for grain alcohol pour a cubic 
centimeter of it into a test tube, denatured will do, and 
add an equal quantity of sodium hydroxide solution. 
Warm the mixture gently and add iodine, a crystal at a 
time until you obtain a yellow precipitate. Smell of 
the contents of the tube. The odor is familiar. 
Where have you detected it before? I think you will 
soon remember that it is the odor so common about a 
hospital. The substance is iodoform, one of the most 
powerful antiseptics known to surgery. This test is a 
delicate one. Very small quantities of alcohol will 
give it. 

Repeat the test on witch hazel, bay rum, extracts, 
and medicines suspected of containing alcohol. If a 
liquid is highly colored, it is best to distil off a little of 
it and test the distillate. 


254 77 *^ Boys’ Own Book of Science 

Test for Formaldehyde.—Before we can make the 
test for wood alcohol, we must learn the test for for¬ 
maldehyde. We do not test directly for wood alcohol 
but convert it first into formaldehyde. This test is 
similar to that of the doctor’s treatment who could 
cure only fits. He first threw his patients into fits and 
then proceeded to cure them. 

Into a glass of milk put one or two drops of a 5 per 
cent solution of formaldehyde. Into a test tube pour 
2 c.c. of concentrated sulfuric acid and add a few 
drops of ferric chloride solution. Then, inclining the 
test tube somewhat, carefully pour down its side a little 
of the milk. The milk will float on the surface of the 
acid. Examine carefully the color at the dividing line 
between the two layers. You will observe a violet 
coloration. Even very minute quantities of formalde¬ 
hyde in milk will give this test. 

To learn the appearance when no formaldehyde is 
present, repeat the test with milk known to be free 
from this substance. This time you will find only a 
brown color instead of the violet. 

Test for Wood Alcohol.—In making this test we 
must oxidize the alcohol into formaldehyde. To do 
this you will need a spiral of heavy copper wire. About 
one end of a lead pencil or small iron rod wind as 
closely together as possible turns of heavy copper wire. 
About No. 14 will be the proper size of wire. Make 
about a 2-inch length of these turns and leave the free 
end extending upward for 8 or 9 inches. 

Fill a test tube a quarter full of wood alcohol and 



Heating the copper spiral preparatory to making the test for wood alcohol. 


255 

















Special Tests 257 

set it inside a bottle half full of cold water (Fig. 31). 
In your Bunsen flame heat the copper spiral until it 
comes to a bright red heat. This forms copper oxide 
on its surface. Immediately thrust the hot spiral into 
the test tube of wood alcohol. Leave it until the boil¬ 
ing ceases. Then repeat the process six times. Note 



that, as you remove the spiral, the copper has a very 
bright luster. The copper oxide which formed on the 
surface has been entirely reduced in oxidizing some of 
the wood alcohol to formaldehyde. 

Into a test tube of milk pour a little of this oxidized 
solution of wood alcohol. Prepare another test tube 
containing 2 c.c. of concentrated sulfuric acid and a 














258 The Boys’ Own Book of Science 

few drops of ferric chloride solution. Then, as be¬ 
fore, carefully pour some of the milk down the in¬ 
clined side of the test tube onto the surface of the 
acid. Again you will obtain the violet color show¬ 
ing the presence of formaldehyde. This time the 
formaldehyde must have come from the wood 
alcohol. 

This test may he made upon a beverage or any other 
liquid suspected of containing this deadly substance. I 
very often receive at my laboratory samples to be 
tested for wood alcohol. You can learn to make the 
test as well as an expert. 

Food Tests.—There is no more important branch 
of analytical chemistry than that of food analysis. 
And this is a kind of analysis which the amateur can 
carry out very successfully. We often wish to know 
which of the three principal kinds of food are present, 
and sometimes whether adulterants have been used. 
Foods are classified as carbohydrates, proteids, and 
fats. Carbohydrates are those foods which contain 
starch and sugars, such as vegetables and cereals. 
“Carbo” means carbon and “hydrate” water. There¬ 
fore a carbohydrate is a compound containing the ele¬ 
ment carbon together with hydrogen and oxygen in 
proportion to form water. Proteids are food sub¬ 
stances containing nitrogen. White of egg, casein of 
cheese, and lean meat are examples. The fats of 
course comprise butter, olive oil, salad dressings, and 
the fat of meats. We shall begin this work with the 
tests for these three principal food constituents. 



Special Tests 259 

Test for Carbohydrates. —We can make a general 
test for carbohydrates and separate tests for particular 
members of this class such as starch, glucose, and cane 
sugar. This test depends upon the fact that a carbo¬ 
hydrate will give a purple color with an alcohol solution 
of alpha-naphthol. This solution may be made by 
dissolving 3 g. of the alpha-naphthol crystals in 25 c. c„ 
of alcohol. Your druggist will be able to supply this 
substance or obtain it for you. 

Pulverize some cereal such as wheat, barley, or rice 
and boil it in a test tube two-thirds full of water. 
Filter this into another test tube and to the filtrate add 
2 c.c. of the solution of alpha-naphthol. Then in¬ 
clining the test tube pour slowly down its side 3 c. c. 
of concentrated sulfuric acid. The acid being heavy 
will slide to the bottom of the tube and between the 
layer of acid and that of the mixture above will appear 
a purple ring. This test may be repeated with po¬ 
tatoes, vegetables in general, sugars, and any other 
food which you wish to test for carbohydrates. 

The Starch Test. —Boil a pinch of starch in a small 
beaker two-thirds full of water. Pour a little of this 
thin paste into a test tube and nearly fill it with water. 
Then prepare a dilute solution of potassium iodide and 
add to it a few crystals of iodine. One gram of iodide 
to 25 c.c. of water will be sufficient. Add a few 
drops of the iodide solution to the test tube containing 
the starch and you will obtain a deep blue color. This 
is the starch test. 

Cut a potato and place a drop of the iodide solution 


260 The Boys’ Ozvn Book of Science 

directly upon the freshly cut surface. A blue color will 
result. This test may be repeated with any other 
starchy food. 

Starch in Ice Cream.—Starch is frequently used in 
ice cream. In small quantity this is desirable but in an 
excessive amount starch is an adulterant. Place a 
little of the ice cream in a test tube and boil it with 
io c. c. of water. Let it cool and add a few drops of 
the iodine solution. If starch is present, the tell-tale 
blue will appear. 

Glucose.—Glucose is one of the two principal sugars 
and an important carbohydrate. It is used in great 
quantities in the manufacture of confections, and it is 
obtained commercially from starch for the manufac¬ 
ture of alcohol. To make the glucose test you will 
need two solutions known as Fehling’s solutions. 
These solutions are prepared as follows: 

Solution No. i : 17 g. of copper sulfate in 250 c.c. 

of water. 

Solution No. 2: 86 g. of Rochelle salts and 25 g. 

of sodium hydroxide in 250 c.c. of water. 

Now dissolve a little glucose in a half test tube full 
of water and add 1 c.c. of each solution. A deep blue 
color will at first form. This color is characteristic 
of copper solutions in the presence of an alkali. But 
heat the contents of the tube and the blue will change 
to a bright brick red. This is the test for glucose. 

You may easily test confections, honey, maple syrup, 
molasses, jam, and jelly for glucose. Dissolve a 


Special Tests 261 

little of the sample in water and apply the test as 
above. 

Cane Sugar.—What we usually speak of as sugar 
comes from the cane. Try the glucose test on this 
sugar. You will be unable to obtain the red precipitate 
this time. Empty out the mixture, dissolve a little 
cane sugar in half a test tube of water, and add one 
drop of concentrated hydrochloric acid. Heat this a 
few moments at nearly the boiling temperature, moving 
the test tube back and forth through the flame so as not 
to develop a small geyser and shoot the contents of 
the tube onto yourself or the table. (This is always 
rulable in heating a test tube containing a solution.) 
Then apply the Fehling test. This time you will ob¬ 
tain the red precipitate of cuprous oxide showing that 
the cane sugar has been changed into glucose. The 
hydrochloride acid causes each molecule of cane sugar 
to unite chemically with a molecule of water and split 
into two molecules of the lower form of sugar. This 
process is known as the “inversion of cane sugar.” 

Conversion of starch into glucose may also be 
accomplished in the same way. To 1 g. of starch in 
10 c.c. of water add 3 or 4 drops of hydrochloric acid 
and boil for ten minutes. Again apply the Fehling solu¬ 
tion and you will obtain the test for glucose. 

Tests for Fats.—To test for a fat we must dissolve 
it in some liquid such as benzol or gasoline. To a few 
drops of olive oil in a test tube add 3 or 4 c.c. of gaso¬ 
line and set the test tube in a beaker of hot water. Let 
it stand for several minutes, shaking it occasionally, 


262 The Boys’ Own Book of Science 

and then pour a few drops of the solution onto a folded 
filter paper placed in the funnel. After the gasoline 
has evaporated, examine the paper. A grease spot 
will appear, which can be plainly seen if held to the 
light. 

Finely divide any food which you wish to test, warm 
it for some time with gasoline, and filter. (Keep 
gasoline away from the flame ) and do not warm the 
mixture over a flame.) 

Test for a Proteid.—To make this test you will 
need a special reagent. It is prepared by mixing cop¬ 
per sulfate and potassium hydroxide solutions. Dis¬ 
solve 3 g. of copper sulfate in 100 c.c. of water and 10 
g. of potassium hydroxide in another 100 c.c. Add 
the copper sulfate solution to that of the hydroxide a 
drop at a time until a faint blue color is obtained. 

Place tw r o porcelain dishes side by side on your table. 
In the first put a small quantity of finely divided peas 
or lean meat. Cover it with 5 c.c. of the above 
reagent, and in the second dish place an equal quantity 
of this reagent for purposes of comparison. The solu¬ 
tion in the dish in which you are making the test will 
become pink or violet in color. T his coloration will 
be readily seen by comparing the solutions in the 
two dishes. This test may be repeated on any food¬ 
stuff. 

Baking Powders.—The purpose of baking powder 
is to liberate carbon dioxide gas and cause the bread or 
cake to become light and porous. All baking powders 
contain sodium bicarbonate, which is ordinary baking 


Special Tests 263 

soda, and some acid substance to react with it and 
liberate the carbon dioxide. 

Add a little water to some baking powder in a test 
tube and pour the gas that forms downward into an¬ 
other test tube containing 2 or 3 c.c. of limewater. 
Shake the limewater tube and note the white precipi¬ 
tate. This is proof, as you know, of carbon dioxide. 

Three acid compounds are used in the preparation 
of baking powders. ‘They are cream of tartar, alum, 
and calcium acid phosphate. Cream of tartar is best, 
for it is a fruit acid, coming from grapes, and not 
harmful. Dissolve a little cream of tartar in water 
and test the solution with blue litmus paper. The red 
color shows the acid character of this salt. Add to 
the solution a pinch of baking soda and note the vigor¬ 
ous effervescence of carbon dioxide. Make a mixture 
of about equal parts by bulk of baking soda and cream 
of tartar. Place some of it in a test tube and add 
water. The result shows that you have real baking 
powder. 

Make two other mixtures, one containing baking 
soda and finely pulverized alum and the other baking 
soda and acid phosphate, known as monocalcium phos¬ 
phate. Add water to these, and again you will obtain 
carbon dioxide. 

Testing for Tartrates.—To learn this test dissolve 
a crystal of silver nitrate in 5 c.c. of water and add 2 
drops of ammonia water. Shake a little cream of tar¬ 
tar in half a test tube of cold water. Filter and add 
1 c.c. of the filtrate to the silver nitrate solution. 


264 The Boys’ Own Book of Science 

You will obtain a beautiful mirror of silver upon the 
inside of the test tube. Repeat this test with baking 
powders. You can readily tell whether or not they 
contain cream of tartar. Shake about 4 g. of the 
baking powder with a test tube of water, filter, and 
make the silver nitrate test as described. 

Testing for Alum.—Most of the cheap baking pow¬ 
ders contain alum. Dissolve a little alum in water and 
test the solution with blue litmus paper. Do you not 
see why it can be used to liberate carbon dioxide? 

To learn one test for alum scoop out a small hole on 
the end of a charcoal stick. Place in it a little alum 
and moisten with a drop of water. Adjust your Bun¬ 
sen burner flame so that it is about 2 inches high and 
colorless. Holding the charcoal stick in the left hand 
at the side of the flame and a blowpipe in the right, 
direct the flame upon the alum and heat it vigorously 
for several minutes. Then moisten the residue with a 
few drops of cobalt nitrate solution and reheat with 
the blowpipe. After the second heating, you will 
obtain a blue color. Repeat this test with a baking 
powder. If alum is present, the blue color will appear. 

Another test for alum may be made by heating a 
small quantity of baking powder as strongly as possible 
in a porcelain crucible for some time. Use the full 
heat of the burner. Place the residue in a beaker and 
add boiling water. Let the beaker stand for a few 
minutes and filter, catching the filtrate in another small 
beaker. Add to the filtrate a strong solution of am¬ 
monium chloride, ordinary sal ammoniac. If alum is 


Special Tests 265 

present, a white “flocculent,” or floating, precipitate 
will appear. You will also obtain the odor of 
ammonia. 

Testing for Calcium.—If we find calcium present in 
a baking powder, we may be quite sure that it comes 
from monocalcium phosphate, so often used as the acid 
constituent. Shake a little of some baking powder 
with a test tube of water, filter and to the filtrate add a 
few drops of ammonium oxalate solution. If a white 
precipitate forms which is insoluble in acetic acid, but 
soluble in hydrochloric acid, calcium is present and 
undoubtedly the phosphate too. If you like, you may 
make the ammonium molybdate test for phosphates, 
described under the chapter on water. 

Starch is usually present in baking powder as a 
filler and to take up the moisture absorbed from the 
air so that a powder kept in a box not air-tight will not 
deteriorate so rapidly. Make the iodine test already 
described. 

Sulfates are always present in alum baking powders 
and may be in others. To test for them dissolve some 
of the powder in cold water, filter, and add hydro¬ 
chloric acid to the filtrate a little at a time as long as 
effervescence continues. Then add a few drops of 
barium chloride solution. A white precipitate shows 
the presence of sulfates. 

Ammonium salts are sometimes present as an adul¬ 
terant. To 5 c.c. of the filtrate from a solution of 
baking powder add an equal quantity of a fairly strong 
solution of sodium hydroxide and heat. Hold in the 


266 


The Boys 1 Own Book of Science 

escaping steam a piece of moist red litmus paper. 
If the paper turns blue, ammonium salts are 
present. 

Milk and Butter.—There is no more important arti¬ 
cle of food than milk, and yet it is frequently adulter¬ 
ated. You may easily prove the presence of all three 
of the principal food constituents in milk. To test for 
proteid it will be necessary to curdle some milk. Pre¬ 
pare the curd by mixing 25 c.c. of sweet milk with 175 
c.c. of water and adding very slowly and with constant 
stirring 40 c.c. of a one and one-half per cent solution 
of glacial acetic acid. (Get your druggist to prepare 
this solution for you.) After 20 minutes, filter into a 
clean beaker and save the filtrate. To the curd upon 
the filter paper apply the test for a proteid already 
described. 

Test some of the filtrate for sugar with Fehling’s 
solutions. The red precipitate at once shows the 
presence of this carbohydrate. 

The production of butter from milk proves the pres¬ 
ence of fats. 

Artificial coloring matter is often added to milk to 
give it a rich creamy appearance. To test for annatto 
stir into a sample of the suspected milk baking soda 
until it will just turn red litmus paper a faint blue. 
Then immerse a filter paper in the milk and allow it to 
remain for 12 hours. If annatto is present, the paper 
will be stained a reddish-yellow r . A coal tar dye is 
sometimes used. To detect it add 10 c. c. of hydro¬ 
chloric acid to an equal volume of milk and mix thor- 


Special Tests 267 

oughly. If azo orange } the color usually employed, is 
present a pink coloration will appear. 

Milk Preservatives.—No other form of illegal adul¬ 
teration is more common than to use chemicals to pre¬ 
vent milk from souring. The test for formaldehyde 
has already been given in connection with wood alcohol. 

Ordinary baking soda is often used as a preserva¬ 
tive. In a porcelain crucible evaporate 5 c.c. of the 
milk to dryness on a water bath or over a very small 
flame. Then, heating the crucible with the full heat of 
the burner, convert the residue into an ash. When the 
crucible has cooled pour upon the ash a few drops of 
hydrochloric acid. If you obtain effervescence, sodium 
bicarbonate is present. Save the residue. 

Borax and boric acid are very often used as milk 
preservatives. Dissolve the residue from the previous 
test in as little water as possible and dip into the solu¬ 
tion a strip of turmeric test paper. Holding the paper 
with tongs high above the flame dry it with very gentle 
heat. If either borax or boric acid have been used the 
paper will turn to a cherry red color. Upon the addi¬ 
tion of ammonia, the color will become olive green. 

Oleomargarine.—The simplest test for this very 
common substitute for butter consists in heating some 
of the sample in an iron spoon. Pure butter will melt 
quietly with the production of a large quantity of foam. 
Oleomargarine will sputter, but produces scarcely any 
foam. 

You may also make the following test: Heat 50 c.c. 
of milk in a beaker nearly to boiling and add 5 g. of 


268 The Boys’ Own Book of Science 

butter to be tested. Stir the butter with a match stick 
until the fat has all melted. Then set the beaker in a 
basin of ice water and stir the mixture until the fat 
becomes solid. If the sample is oleomargarine, it will 
collect as a solid mass on the stick. If it is butter, 
the fat will remain suspended in the milk. 

Coal tar dyes are often used to color butter. To 
50 c.c. of water add a few cubic centimeters of alcohol, 
a teaspoonful of butter, and a pinch of cream of tartar. 
Immerse in the mixture some threads of white silk or 
wool and heat to boiling. If coal tar colors are pres¬ 
ent, the fibers will be dyed. 

Saccharin is often illegally used as a substitute for 
sugar. It is a coal tar product and 500 times as sweet 
as cane sugar. To detect it in canned goods or any 
other foodstuff, shake the sample with a little water, 
filter, and add chloroform to 2 or 3 tablespoonfuls of 
the filtrate. Shake the mixture thoroughly and with 
a medicine dropper remove some of the chloroform, 
which, since it does not mix with water, will settle to 
the bottom. Place the chloroform in your evaporating 
dish and heat it to dryness on the water bath. Taste 
of the residue. If it is sweet, saccharin is present. 
Sugar will not dissolve in chloroform, but saccharin 
will. 

To test the quality of vinegar evaporate almost to 
dryness a half teacup of vinegar in a small agate basin. 
Smell of the residue. If you obtain a distinct odor of 
baked apples, the sample is cider vinegar. If you get 
the odor of grapes, it came from wine. A malt vinegar 


Special Tests 269 

will give the odor of malt. If there is no residue, the 
vinegar has been made artificially from acetic acid, 
water, and a little flavoring matter. 

Lemon extract often contains no genuine lemon oil. 
You can determine this by adding 2 c.c. of the extract 
to 50 c.c. of water. If lemon oil is present, there will 
be a milky appearance to the mixture. By the amount 
of this milkiness you will be able to judge of the quan¬ 
tity of lemon oil. If the mixture remains clear, no 
lemon oil is present. 

Vanilla extract is often artificial. To determine 
whether it has actually been made from the vanilla 
bean, dissolve 3 g. of lead acetate in 10 c.c. of water 
and add an equal volume of the extract. If the ex¬ 
tract is genuine, a heavy precipitate will form and 
settle to the bottom, leaving a clear liquid above. 

The purity of olive oil may be determined by shak¬ 
ing 5 c.c. of the oil with 5 c.c. of concentrated nitric 
acid. If the oil is pure a pale green color will be 
obtained within a few minutes. If a brown, red, or 
orange color is obtained, the oil has been adulterated. 
Hold the test tube in a beaker of hot water for 5 
minutes. If the oil is pure, the color will change to 
orange yellow. Peanut oil gives with nitric acid a 
pale rose color, which changes to brownish yellow on 
heating. Cottonseed oil gives a yellowish brown, 
changing to reddish brown. 

Copper salts are often used in canned goods to give 
them a green color. To detect them strongly heat 10 
g. of the sample in a porcelain crucible until an ash has 


270 The Boys’ Own Book of Science 

been obtained. Dissolve the residue by heating it with 
a little nitric acid. Evaporate the solution nearly to 
dryness, and dissolve it in 5 c.c. of water. Pour the 
solution into a test tube and add ammonia water. If 
copper is present, a deep blue color will be obtained. 

Sulfites in canned goods serve two purposes. They 
bleach them and preserve them. Thoroughly pulver¬ 
ize 25 g. of the sample and put it into an Erlenmeyer 
flask. Add 5 g. of pure zinc and 10 c.c. of pure 
hydrochloric acid. Heat the flask gently and hold in 
the neck of it a strip of filter paper which has been 
moistened with a solution of lead nitrate or acetate. 
If sulfites have been used, the paper will become 
brownish to black in color. 

Potassium nitrate, or saltpeter, is a common meat 
preservative. Get your druggist to prepare for you 
a small volume of a 1 per cent solution of diphenyla- 
mine in strong sulfuric acid. Put some of the 
meat in an evaporating dish and add to it 2 c.c. of 
this solution. If nitrates are present, a blue color 
appears immediately. 


Chapter 30 

GEORGE WESTINGHOUSE 


G eorge Westinghouse was another lad whose 
chief delight was in using tools. In the loft 
of his father’s machine-shop at Schenectady, New 
York, he fitted up an “inventor’s” laboratory in which, 
while still a boy, he built a rotary steam engine, with 
which he ran a boat on the Erie Canal. After he had 
become a man he patented this engine. But his father, 
a somewhat stern man of Dutch ancestry, did not 
approve of these boyish pursuits and wished George 
to work at the bench on worth-while projects. Still 
experiment and invent he would. One day his father 
led him to a pile of pipe, which he wished cut into 
pieces of a certain length. Wishing to escape the 
drudgery, George set his inventive brain to work and 
soon had a combination of tools which, when hitched 
to a power-shaft, automatically fed the pipe and cut 
it into the desired lengths. And all through life he 
could devise machinery to do exactly what he wanted 
it to do. 

In 1861, when only fifteen, he attempted to run 
away and go to war. Foiled by his father, he waited 
two years and then enlisted. After the war he en¬ 
tered college, but study did not appeal to him, and 

he soon abandoned school for a life of invention. A 

271 


272 The Boys y Own Book of Science 

couple of railroad accidents led to his two most im¬ 
portant early inventions. One was a patent car-replacer 
for quickly putting derailed cars back onto the track. 
The other was his world-famous air brake. The latter, 
one of the most important inventions ever made, was 
perfected before he was twenty-two. It brought him 
great wealth and made his name known on two con¬ 
tinents. Thus at the very outset of his career he had 
supplied himself with abundant funds for further ex¬ 
perimentation, and that was the passion of his life. 

Under his direction the engineers in his immense 
laboratories and shops developed some of the epoch- 
making inventions of modern times. It was Westing- 
house who saw, as no other man did, the future 
necessity for the manufacture and distribution of alter¬ 
nating-current power. His engineers brought out the 
transformer, the rotary converter, and the induction 
motor, indispensable to the electrical age in which we 
live. He electrified the World’s Fair in Chicago in 
1893 and built and installed the huge generators at 
Niagara Falls, the world’s first big hydro-electric 
plant. He developed the interlocking block system of 
railroad signaling in America. On his private estate 
near Pittsburgh he put down the first of the big Penn¬ 
sylvania gas wells and organized the Pennsylvania Gas 
Company. 

From the days of his boyish contrivances to the end 
of his years Westinghouse was always an inventor, a 
wonderful man, equaled by few and surpassed by none 
in his chosen field. 


Chapter 31 

MORE REAL ANALYSIS 

I N this chapter I wish to give sufficient instruction 
to enable you to do a great deal of original analyti¬ 
cal work. When you have made the tests which I shall 
describe, you should be able to take any of the ordinary 
metallic compounds and determine with perfect cer¬ 
tainty what metal it contains and from what acid it 
has been derived. 

Some of these tests we have already made, but it 
will be best to summarize them with the new ones now 
to be given. When you identify a salt it is necessary 
to do two things—determine the metal it contains and 
the acid radical with which it is combined. We shall 
state first as briefly as possible the tests for the more 
important acid radicals. In every case you should re¬ 
peat the test with a known sample of the salt. 

Chlorides.—Dissolve a little sodium chloride, in 
water and add a solution of silver nitrate. You will 
obtain a white precipitate of silver chloride which will 
not dissolve in dilute nitric acid. 

Bromides.—For the bromide test you will need a 
solution of chlorine water. This must be freshly pre¬ 
pared. Before starting remember that chlorine is 
poisonous. Put your apparatus near an open window 

273 


274 The Boys } Own ,Book of Science 

or in a good draft and do not breathe the gas. But, 
in preparing it on the small scale which we shall em¬ 
ploy, just be careful and there will be no danger. Fit 
a test tube to a one-hole stopper and delivery tube. 



Figure 32. 

Set-up for preparing chlorine water. 


Clamp it to the ring-stand and removing the stopper 
place in the test tube 5 c.c. of concentrated hydro¬ 
chloric acid. Sift into the acid a teaspoonful of 
manganese dioxide and replace the stopper. Let the 
delivery tube pass to the bottom of a small bottle filled 
with water (Fig. 3 2 )* Now heat the test tube very 







































Preparing chlorine water for use in testing iodides and bromides. 


275 














277 


More Real Analysis 

gently and a stream of chlorine gas will be driven off. 
Be careful not to heat the tube strongly enough to 
drive its contents over into the delivery tube. As the 
chlorine bubbles through the water, some of it dis¬ 
solves and soon the water becomes greenish in color. 
When this happens, turn off the burner, remove the 
delivery tube and preserve the chlorine water in a 
stoppered bottle. The bottle should be dark colored, 
because otherwise the chemical rays of the sun cause 
the chlorine to unite with the water, and the strength 
of the solution becomes very weak. 

To make the bromide test dissolve a little sodium 
or potassium bromide in half a test tube of water and 
add a few drops of chlorine water. Immediately 
you will observe that the solution turns brown. This 
is because the chlorine has set bromine free, since 
chlorine is more active than bromine. Now add a 
cubic centimeter of carbon disulfide and placing your 
thumb over the mouth of the tube shake the mixture 
vigorously. You will observe that the carbon disulfide 
becomes reddish in color and settles to the bottom of 
the tube. The bromine has dissolved in it and colored 
it. Any other bromide will give a similar test. 

Iodides.—The test for an iodide is exactly the same 
as that for a bromide. Dissolve a particle of po¬ 
tassium iodide not larger than a pin head in two-thirds 
of a test tube of water. Add to the solution a few 
drops of chlorine water. Again a brown color ap¬ 
pears. Add a cubic centimeter or two of carbon disul¬ 
fide and shake. This time you will find that the carbon 


278 The Boys’ Own Book of Science 

disulfide becomes colored a rose to violet hue. If the 
color is very dark too much iodide has been used. 

Instead of using carbon disulfide, you may also pour 
some of the solution to which you have added chlorine 
water into water containing starch paste. A deep 
blue color will appear. 

Sulfides.—To a fragment of iron sulfide in a test 
tube add either dilute hydrochloric or sulfuric acids. 
You will very soon obtain the foul smelling odor of 
hydrogen sulfide gas. It is the odor with which you 
are already familiar as coming from bad eggs. But 
you must make a chemical test too. Hold in the 
escaping gas a piece of filter paper moistened with 
lead nitrate solution. Immediately the paper will 
become black. Lead sulfide has formed. 

Sulfites.—To a half teaspoonful of sodium sulfite 
in a test tube add hydrochloric acid. You will get 
the sharp odor of sulfur dioxide. Pour the gas care¬ 
fully down into a test tube containing a dilute solution 
of potassium permanganate. The purple color of the 
permanganate will immediately disappear. 

Sulfates.—Dissolve a little of any sulfate in water 
and add a few drops of a dilute solution of barium 
chloride. A white precipitate of barium sulfate will 
form, which is insoluble in dilute hydrochloric acid. 

Nitrates.—Prepare a rather strong solution of fer¬ 
rous sulfate. Place 2 c.c. of it in a test tube and care¬ 
fully pour down the side of the tube, held in an inclined 
position, an equal volume of concentrated sulfuric acid. 
Being heavy the acid will pass to the bottom and lift 


More Real Analysis 279 

the sulfate solution above it. Now pour down the 
side of the test tube a cubic centimeter of a dilute 
solution of sodium or potassium nitrate. A brown 
ring will appear at the dividing line between the two 
layers, which will widen by careful shaking and then 
disappear. 

Carbonates.—To a little baking soda, washing soda, 
or marble in a test tube add hydrochloric acid and pour 
the gas into limewater. (Do not let the liquid pass 
into the limewater too.) Shake the tube and, as 
usual, you will obtain a white precipitate. 

Phosphates.—To a solution of sodium phosphate 
add 2 c.c. of the ammonium molybdate solution, pre¬ 
pared in the work on water, and warm gently. A 
lemon-yellow precipitate will appear. 

Oxalates.—Dissolve some sodium or potassium oxa¬ 
late in water and add a solution of calcium chloride. 
A white precipitate will form which does not dissolve 
in acetic acid but will dissolve in hydrochloric acid. 
If an oxalate in solid form is heated in a test tube 
carbon monoxide gas will escape and burn with a blue 
flame at the mouth of the test tube. 

Tartrates.—Heat some cream of tartar in a por¬ 
celain crucible until it darkens and gives the odor of 
burnt sugar. Dissolve another portion in half a test 
tube of water. To 5 c.c. of dilute silver nitrate solu¬ 
tion add 1 c.c. of the cream of tartar solution and 2 
drops of ammonia and warm. Metallic silver will be 
precipitated on the inside of the test tube. 

Chlorates.—Heat a little potassium chlorate in a 


280 The Boys’ Own Book of Science 

test tube and thrust into the tube a glowing splint. It 
will be kindled into a flame. 

Acetates.—Place enough sodium acetate in a test 
tube to fill the curved portion. Add 2 or 3 drops of 
water and an equal quantity of concentrated sulfuric 
acid. Warm and add a few drops of grain alcohol. 
You will obtain a rather pleasant fruit odor. 

Permanganates.—Dissolve a single crystal of po¬ 
tassium permanganate in half a test tube of water 
and add a solution of sodium sulfite. The purple 
color of potassium permanganate will disappear. 

Chromates.—To a solution of potassium chromate 
add barium chloride solution. A yellow precipitate 
forms which is soluble in hydrochloric acid. If alcohol 
is added to the solution, the color becomes green. 
Lead nitrate solution will also give chrome yellow 
with a chromate. 

Borates.—To half a test tube of borax add 3 c.c. 
of concentrated hydrochloric acid and dip into the 
solution a piece of turmeric paper. Holding the paper 
high over the flame dry it. A cherry red color will 
appear which changes to olive green when ammonia 
Is added. 

Moisten some borax powder with hydrochloric acid 
in an evaporating dish and add alcohol. Ignite the 
alcohol, and in a few moments you will observe a 
green colored flame. 

Tests for the Metals.—The tests just described in¬ 
clude most of the acid radicals which you will en¬ 
counter. We must now learn tests for the more 





More Real Analysts 281 

common metals. The work being described in this 
chapter is not systematic qualitative analysis, but it 
will give you an excellent start toward it. 

Flame Tests.—Sodium, potassium, lithium, calcium, 
barium, and strontium may be detected by the colors 
that they give to the Bunsen flame. For this work 
you will need a platinum wire, although a nickel wire 
may be substituted. Platinum of course is expensive, 
but you will need a piece only 3 inches long. When 
you get it seal it into the end of a small glass tube about 
as long as the wire. Hold the end of the tube in the 
flame and thrust about a quarter of an inch of one 
end of the wire inside the tube. Slowly turn the tube 
and as the glass melts it will run together and make 
a perfect seal. 

Dip the wire into concentrated hydrochloric acid 
and hold it in the outer, oxidizing, flame of the Bunsen 
burner. Repeat this once or twice to clean the wire. 
When the wire is clean, the flame should be colorless. 

Have at hand solutions of the salts of the six metals 
named above. Dip the clean platinum wire into the 
solution of sodium and hold it in the outer flame. A 
deep yellow color results. This is the characteristic 
test for sodium. 

Clean the wire as described above and dip it into 
a solution of potassium salt. If the solution is pure, 
you will obtain a violet colored flame. Often sodium 
is present, and, if so, even in minute quantity, the 
violet of potassium will be completely masked by the 
yellow of sodium. Therefore, whenever testing for 


282 


The Boys’ Own Book of Science 

potassium, look at the flame through two thicknesses 
of blue glass. The glass will allow the violet 
color of potassium to pass through it, but not the 
yellow of sodium. Repeat the test until you are sure 
of it. 

Make the test for each of the other four metals, 
cleaning the wire after each test. Lithium will give a 
beautiful carmine red, calcium gives an orange, 
strontium a bright red, and barium green. 

Hold a piece of glass tubing in the flame until it 
softens. The yellow color of sodium is obtained, for 
sodium compounds are used in the manufacture of 
glass. 

Borax Bead Tests.—A number of other metals are 
detected by the colors which they give when fused with 
a borax bead. For these tests, too, you will need the 
platinum wire. Make a small loop on the end of the 
wire, heat the loop in the outer flame of the burner 
and dip it into borax powder. Some of the powder 
will cling to the wire. Thrust this into the flame and 
heat it until the powder fuses and runs into a clear 
glassy bead which completely fills the loop. To ob¬ 
tain such a bead the loop must be small. 

Touch the hot bead as lightly as possible to a crystal 
of cobalt nitrate, and reheat in the flame until the 
cobalt compound completely fuses with the bead. 
Allow the bead to cool and note that you have a deep 
blue color. Cobalt will always give this color. 

To clean the wire, heat it in the flame and thrust 
the hot bead into water. With your fingers remove 


More Real Analysis 283 

the material on the wire and, making another loop, 
prepare a fresh bead. If the bead is not colorless, 
another must be made. 

Using the substances in solid form, repeat the test 
with compounds of copper, chromium, iron, nickel, 
bismuth, and manganese. In each case characteristic 
colors will be obtained which you should note and 
record. In some instances the color is different when 
the bead is hot from what it is when cold. Manganese 
gives an amethyst red, but only a tiny speck of the 
compound should be used. 

Cobalt Nitrate Tests.—In the end of a charcoal 
block scoop out a small hole and place in it a little 
of some zinc compound. Moisten this powder with 
a drop or two of water and, using a small Bunsen 
flame, heat it strongly with the blowpipe for several 
minutes. Moisten the residue with a drop of cobalt 
nitrate solution and reheat with the blowpipe. Zinc 
gives a green color after the second heating. 

Repeat the test using compounds of aluminum and 
magnesium. Alum may be used for the first and 
Epsom salt for the second. In one case you will ob¬ 
tain a blue color after the second heating and in the 
other a rose color. 

Other Blowpipe Tests.—Make a mixture of pow¬ 
dered blue vitriol and washing soda or baking soda. 
Heat some of the mixture on a charcoal block with 
the blowpipe. Globules of metallic copper will be ob¬ 
tained. Silver nitrate will give white shiny globules 
of silver. 


284 The Boys’ Own Book of Science 

Compounds of lead and tin, when heated in the 
same way, will give malleable beads of metal and a 
deposit on the charcoal. Antimony and bismuth give 
brittle beads and a deposit. 

Iron Tests.—Prepare dilute solutions of any fer¬ 
rous and ferric salts that you may have. For indi¬ 
cators prepare dilute solutions of potassium ferro- 
cyanide, potassium ferricyanide, and potassium sulfo- 
cyanate. 

Add a cubic centimeter of the ferric solution to two- 
thirds of a test tube of water and test with a few drops 
of potassium ferrocyanide indicator. You will obtain 
a deep blue color. The ferrous salt gives a light blue 
with this indicator. 

Test both salts with each of the other indicators. 
Use very dilute solutions each time, for these are 
delicate tests. I think you will find that the ferro¬ 
cyanide and sulfocyanate tests are best for a ferric 
salt and the ferricyanide test for a ferrous salt. 

Many soils and rocks contain iron compounds. 
Wherever you see a red or yellow color, iron is prob¬ 
ably present. To test for it place a little of the rock 
or soil in a test tube and boil it with concentrated 
hydrochloric acid. Filter and test the diluted filtrate 
with potassium ferrocyanide or potassium sulfocyanate. 
The color obtained will be the evidence.. 

Lead, Silver, and Mercury.—These metals form the 
first group in the systematic separation of the metals 
and their detection in qualitative analysis. 

To 5 c.c. of a solution of lead nitrate add hydro- 





Making a blowpipe test for a metal. 


285 





• / 




More Real Analysis 287 

chloric acid as long as a precipitate seems to form. 
Allow the precipitate to settle and add another drop 
of acid to the clear liquid above. If all of the lead 
has been precipitated, no more precipitate will form. 
When this is the case, pour off the clear liquid. Fill 
the test tube with cold water, shake and let the precipi¬ 
tate settle. Pour off the clear liquid and fill the test 
tube with hot water. You will find that the precipitate, 
which is lead chloride, dissolves in hot water but not 
in cold. 

Repeat this procedure with silver nitrate solution. 
When you have determined that the silver chloride, 
which forms, does not dissolve in hot water, add to 
some of the precipitate ammonia water. This readily 
dissolves it. 

Make the same tests with a solution of mercurous 
nitrate. I say “mercurous” because there are two 
series of mercury salts and only the “ous” salt belongs 
in this group. I think you will find that neither hot 
water nor ammonia dissolves mercurous chloride. But 
you do find that ammonia turns it black. 

Now you have the means of detecting and separat¬ 
ing these three metals. 

To separate lead, silver, and mercury place in a 
small beaker 5 c.c. each of solutions of lead, silver, and 
mercurous nitrates. Add a liberal quantity of dilute 
hydrochloric acid and filter into a clean beaker. To 
determine whether enough acid has been added put a 
few drops of it into the filtrate. If no more precipi¬ 
tate forms, enough has been added. But, if a precipi- 


288 


The Boys’ Own Book of Science 

tate does form, add more acid and filter again. Re¬ 
peat this until the precipitation is complete. Wash 
the precipitate upon the filter by passing cold water 
through it a number of times. Then pass hot water 
through and catch the filtrate in a clean test tube. 
From the previous tests, which chloride should be dis¬ 
solved? Add to the filtrate a little potassium chrom¬ 
ate solution. The yellow precipitate of “chrome 
yellow” proves that lead has been separated. There 
now remain on the filter the chlorides of silver and 
mercury. 

To separate the silver and mercurous chlorides pour 
through the filter 5 c.c. of ammonia water catching 
the filtrate. A black residue appears on the filter. 
You will recognize this as the mercury compound. 
Add to the filtrate dilute nitric acid and a white pre¬ 
cipitate will form. By the neutralization of the am¬ 
monia the silver chloride, which dissolved and passed 
into the filtrate, has been re-precipitated. You have 
now completed the separation of the metals of 
Group I. 

Using the various tests given in this chapter you 
will find it most interesting work to identify unknown 
compounds. If you have a chum who is working with, 
you, each may give to the other unknown substances 
to analyze and report upon. 

Organic matter may be detected by heating the sub¬ 
stance in a porcelain crucible. If such matter is pres¬ 
ent, the substance will char. 


Chapter 32 
CRYSTALS 


C rystal forms of matter are among the most 
beautiful to be found in nature. Diamond is 
crystallized carbon. Sir Humphry Davy burned a 
diamond in pure oxygen and obtained nothing but 
carbon dioxide. Others have repeated the experiment 
many times since. Snowflakes are crystals formed by 
the condensation of water vapor at temperatures be¬ 
low freezing. The mineral wealth of the earth has 
been deposited in crystal form during the countless 
ages of the past. Beautiful specimens of gypsum, 
quartz, Iceland spar, and alumina bear evidence of 
nature’s handiwork. By what processes precious 
metals have come to be embedded in veins of crystal 
rock we can only guess. But crystals disclosing, under 
the microscope and often to the unaided eye, definite 
geometric shapes abound in the earth’s crust and may 
be prepared by artificial means. 

In the laboratory we may prepare crystals by cool¬ 
ing hot saturated solutions. The process of crystalliza¬ 
tion is one of the most important in the purification 
of chemical compounds. It was as the result of a 
prodigious amount of crystallization and recrystal¬ 
lization many times repeated that Madame Curie 

289 


290 The Boys’ Own Book of Science 

separated from several tons of pitchblende a few 
hundredths of a gram of the element radium, a mil¬ 
lion and a half times more active than the parent 
mineral itself. The Chili saltpeter of South America 
and the potash from the famous Stassfurt deposits of 
Germany are purified by crystallization. Cream of 
tartar is separated by crystallization from the crude 
salt which deposits on the inside of grape juice casks. 
There are many other illustrations. 

Preparation of Crystals.—Obtain some dry pow¬ 
dered washing soda. Heat 50 c.c. of water to boiling 
in a small beaker. Sift the washing soda into it with 
constant stirring as long as the salt will dissolve. When 
a little remains that will not dissolve after further 
boiling, allow the solution to cool. As it does so, 
crystals will form. After the solution has cooled for 
several hours, pour off the liquid, and place the crystals 
upon a filter or blotting paper. 

When dry, heat a few of the crystals in a dry test 
tube, inclining the mouth of the tube downward some¬ 
what. Note that water forms and that the salt loses 
its crystal appearance. Evidently the crystal form is 
due to the presence of water. This water is chemically 
combined with the salt and known as water of crys¬ 
tallization. Expose some of the crystals to the 
air for a few hours and observe that they become dull 
and white on the surface, losing their bright crystal¬ 
line appearance. After a time you will be able to 
crumble them to a powder with your fingers. Such 
salts which give off their water of crystallization and 


Crystals 291 

crumble to a powder upon exposure to the air are 
called efflorescent salts. 

Dissolve as much potassium nitrate as possible in 
25 c.c. of hot water. Allow the mixture to cool and 
you will obtain a mass of crystals. These two experi¬ 
ments also illustrate the fact that most salts are more 
soluble in hot water than they are in cold. Repeat 
with Epsom salt. 

In a dry test tube heat a crystal of copper sulfate. 
Water will be driven off, the blue color will disappear, 
and, when cold, you will be able to crush the salt to 
a dry powder between your fingers. Dissolve this 
powder in a few drops of hot water, place it in your 
evaporating dish, and let it stand. The blue crystals 
will reappear. 

Just as in these cases, many salts depend upon 
chemically combined water for their crystal forms. 
But there are others which do not. Heat some crystals 
of potassium chlorate in a test tube. The crystals 
melt, but no water is formed. Test all the salts which 
you have to see whether they will give off water and 
crumble to a powder. 

If you have a balance, place in one pan a porcelain 
crucible and weigh it very carefully. Then weigh 
into it exactly 2 g. of some salt containing water of 
crystallization. Crystallized barium chloride is an 
excellent salt for this purpose. Place the crucible on 
a clay triangle over the Bunsen burner and heat first 
with a small flame, gradually increasing it to its full 
capacity. Continue the heating for 20 minutes. When 


292 The Boys’ Own Book of Science 

the crucible has thoroughly cooled, reweigh it. The 
weight is less now. Find the loss of weight and deter¬ 
mine the percentage of water of crystallization that 
has been driven off. Repeat this experiment a num¬ 
ber of times. You will find that the percentage loss 
is always the same. This fact proves that the water 
is combined in definite, or chemical, proportions. This 
law of definite proportions is one of the fundamental 
principles of experimental chemistry. 

Sulfur Crystals.—Dissolve a piece of roll sulfur 
about as big as a pea in a little carbon disulfide. 

(Keep the carbon disulfide away from a flame.) 
Pour the solution onto a watch glass and let the liquid 
evaporate. Crystals with diamond shaped faces known 
as rhombic crystals will be left. If you examine 
them with a small lens their shape will be clearly 
seen. 

Sulfur also forms crystals of another shape. Melt 
some roll sulfur in a test tube. Heat the tube very 
slowly and move it about in the flame. Remove it 
from the flame whenever the contents begin to look 
red or dark. It will gradually melt to a clear straw 
colored liquid. Pour this into a folded filter paper. 
Watch the sulfur as it cools and when the surface has 
nearly frozen over, open up the filter, pour out the 
liquid remaining in the center, and you will have a 
mass of needle shaped crystals. They are called mono¬ 
clinic, or prismatic crystals. Examine them with a 
hand lens and you will see that they resemble long 
slender prisms in shape. 



293 


Crystals 

A Lead Tree.—Prepare a fairly strong solution of 
lead nitrate (about io g. to ioo c.c. of water) and 
place it in a cylinder or bottle. Suspend in the solu¬ 
tion a zinc rod covered with a layer of asbestos paper. 
After standing several hours, you will find crystals 
of lead on the outside of the rod and running off 
into the solution like the branches of a tree. 

Preparing “Gold.”—Mix equal parts of powdered 
tin and flowers of sulfur with one-eighth their bulk 
of ammonium chloride powder. Place the mixture 
in a porcelain crucible and cover it with a thin layer 
of the ammonium chloride. Cover the crucible with 
its lid and heat it over the Bunsen burner. A white 
smoke will issue from the crucible due to the vaporiza¬ 
tion of the ammonium chloride and a mass of bright 
crystals resembling gold will appear on the crucible lid. 

Preparation of Alum.—In each of two beakers 
place 200 c.c. of water. In one dissolve 35 g. of po¬ 
tassium sulfate and in the other 68 g. of non-crystalline 
aluminum sulfate. To dissolve them quickly heat the 
beakers gently and with constant stirring. When the 
salts have dissolved, pour the solutions into an agate 
basin, and evaporate off half to two-thirds of the 
water. Then let the mixture cool. A mass of crystals 
will form which consist of a chemical combination of 
the two salts. This double salt is true alum. 

You may grow a large crystal of alum by suspending 
a tiny crystal by means of a thread in a saturated 
solution of the salt. Let the process continue for 
several days. 




294 The Boys’ Own Book of Science 

Supersaturation.—Melt 50 g. of photographer’s 
hypo in a small Erlenmeyer flask or beaker. Allow 
the solution to cool without disturbance. Then add 
a tiny crystal of the same salt and at once the whole 
contents of the flask will become a mass of crystals. 
The salt melts and dissolves in its own water of 
crystallization. If undisturbed, the salt will remain 
in solution, even when cold. But upon the addition of 
a tiny seed crystal it takes back its water of crystalliza¬ 
tion and solidifies. 

Crystals of Iodine.—Place in the bottom of a dry 
test tube 1 g. of potassium iodide mixed with one-fourth 
its bulk of manganese dioxide. Clamp the test tube 
in a vertical position to the ring-stand and pour care¬ 
fully down upon the mixture without wetting the sides 
of the tube 2 c.c. of concentrated sulfuric acid. Warm 
the tube very gently. The violet vapor of iodine will 
at once appear and much of it will condense on the 
cold upper walls of the tube giving crystals of the 
solid. These may be preserved in a tightly stoppered 
bottle or test tube. 

Chemically Pure Sodium Chloride.—As you know, 
sodium chloride is ordinary table salt. As we buy 
it at a grocery store, salt is not pure. You have no¬ 
ticed many times how salt absorbs moisture in damp 
weather. This is due to the presence of small amounts 
of calcium and magnesium chlorides. These are what 
we call deliquescent salts. If you have it, place a little 
of one of them on a watch glass and leave it for a few 
hours. The salt will become moistened on the surface, 



Crystals 295 

and, if left for a day or two it will absorb enough 
water to form a solution. These and other impurities 
are often present in the commercial article. The readi¬ 
ness with which salt dampens is an indication, not only 
of the amount of impurity present, but also of the 
state of humidity of the air. It will be interesting to 
prepare crystals of chemically pure sodium chloride 
and compare its properties with those of ordinary salt. 

Dissolve about 75 g. of ordinary salt in 180 c.c. of 
water, distilled if possible. Filter into a clean beaker 
to remove any dirt and obtain a clear solution. Add 
concentrated hydrochloric acid until a precipitate just 
begins to form. This is sodium chloride, which is 
being thrown out of solution. Now set up a hydro¬ 
chloric acid generator just as was described in the 
chapter on acids, bases, and salts. Place in the gener¬ 
ator a small handful of table salt, or better rock salt. 
Connect the delivery tube to a funnel clamped mouth 
downward to a support and dipping beneath the solu¬ 
tion of sodium chloride held in a beaker or small 
battery jar (Fig. 33). Through the thistle tube of 
the generator pour concentrated sulfuric acid and 
apply heat at once using a small flame. The hydro¬ 
chloric acid gas which passes into the solution being 
more soluble than the sodium chloride will drive this 
compound out of solution as chemically pure salt. Any 
impurities present in it will remain in solution. 

When the precipitation seems to be complete, first 
remove the funnel and then turn off the gas. After the 
salt has settled, pour off the clear liquid. Cover the 


296 The Boys' Own Book of Science 

salt with pure dilute hydrochloric acid and shake well. 
Allow the salt to settle again and pour off the liquid. 



Figure 33. 

The preparation of chemically pure sodium chloride by passing hydro¬ 
chloric acid gas into a saturated solution of the salt. 


Repeat this operation once or twice. Its purpose is to 
wash the crystals free from the liquid clinging to them. 


















































Crystals 297 

Finally filter the salt and allow the crystals to dry. 
You now have chemically pure sodium chloride. 

Place some of it on a watch glass and observe 
whether it becomes moist as ordinary salt does on 
exposure to the air. Examine some of the crystals 
with a lens and note their form. 

A Crystal Garden.—Prepare a solution of ordinary 
water glass such as is used for preserving eggs. This 
solution is obtained by mixing the liquid with water 
until its specific gravity is 1.10. Specific gravity may 
be determined with a hydrometer. Possibly you can 
borrow one from the school laboratory or from a 
druggist. If not, mix the silicate with water until the 
solution is just a little heavier than water. If a little 
of it is poured into a test tube of water it should just 
nicely sink to the bottom. If you can weigh the 
solution, 100 c.c. of it should weigh 110 g. plus, of 
course, the weight of the container. 

Place a pint of this in a battery jar or a large beaker 
and drop into it at various points on the bottom 
crystals of copper sulfate, cobalt nitrate, nickel sul¬ 
fate, manganese sulfate, and ferrous sulfate. Leave 
the jar undisturbed for several days. Gradually there 
will appear from each substance a crystal growth of 
stalk and branches, each “tree” differing in color from 
the others. 

Boiling by Freezing.—In a small flask melt 50 g. 
of crystallized sodium sulfate, known commercially as 
Glauber’s salt. The salt will melt and dissolve in its 
water of crystallization. When the salt has entirely 



298 The Boys’ Own Book of Science 

melted, plug the neck of the flask with cotton wool and 
allow the solution to cool undisturbed. 

Meanwhile make an ether thermometer. To do so 
blow a bulb on the end of a glass tube. You will find 



Boiling ether with the heat liberated by the crystallization of sodium sulfate. 

this an interesting operation, but you will not succeed 
at first. Select a piece of glass tubing about a foot long 
and having as thick walls as possible. Put one end of 
this in the flame and holding the tube in a nearly 
vertical position soften the end and let it fuse into a 
solid mass. When you have formed a solid mass of 








Crystals 299 

molten glass and the opening has been completely 
closed, remove the tube from the flame and gently blow 
into it. If you are careful, you can produce an evenly 
rounded bulb of considerable size. A little practice 
will make you an expert. When you have produced 
a good piece of work, fill the bulb with ether or carbon 
disulfide. You now have an ether thermometer. If 
placed in a liquid having a temperature of 36° C. or 
more, the ether will boil. 

When the solution of sodium sulfate has thoroughly 
cooled, immerse in it the bulb of your thermometer and 
give the flask a quick shake (Fig. 34). The salt will 
turn to a solid mass of crystals and produce enough 
heat to boil the ether and cause it to rise in the tube. 
If you have difficulty in crystallizing the salt by shak¬ 
ing, add a tiny crystal of the salt itself. This gives a 
center about which crystallization may start and will 
do the trick. If you like, you may ignite the ether 
vapor at the top of the tube. 


Chapter 33 

GUGLIELMO MARCONI 

W HEN Marconi, an Italian youth born in 1874, 
was twelve years old, Hertz demonstrated the 
possibility of signaling through space by means of 
ether waves. This discovery created a tremendous 
interest throughout the whole scientific world. But it 
remained for Marconi, while still little more than a 
boy, to make the first revolutionizing application of 
these waves and demonstrate the wonderful possibili¬ 
ties of wireless communication. Patiently he waited 
for the learned scientists in their well equipped labora¬ 
tories to invent and perfect wireless apparatus, but he 
waited in vain. At length he started to experiment 
for himself, and soon he startled the world. 

In his father’s garden he set up aerials and crude 
instruments of his own devising. Then making one 
discovery after another he began actually to send and 
receive signals. At first he could send over distances 
of only a few hundred feet. But he worked over his 
apparatus by day and dreamed of it by night. Such 
enthusiasm and earnest effort were bound to produce 
results, and they did. By 1896 he was sending over 
distances of several miles. Then he went to England 
where he made remarkable demonstrations. He estab- 


300 


3oi 


Guglielmo Marconi 

iished a station on the Isle of Wight and maintained 
communication with the mainland. He sent messages 
from ship to shore and in 1898 reported for a Dublin 
paper the news of the annual Kingstown regatta. He 
established wireless communication across the Channel 
between England and France. 

Then Marconi won his most notable triumph. He 
came to America in 1901. On the coast of Newfound¬ 
land in the strong winds and bitter cold of December 
he raised a huge kite-aerial high in the air and led 
his lead-in wire to simple instruments on a table in an 
upper room of an old barracks. Patiently he waited 
the signal of the letter “S” to be sent from his station 
in Cornwall, England. And presently it came. Un¬ 
mistakably he heard in his telephone receivers the three 
dots of the pre-arranged signal. Transatlantic wire¬ 
less was an established fact, and Marconi, then but 
twenty-six years old, had made a name for himself 
which will never perish. The vision of the boy experi¬ 
menter had been translated into a wonderful achieve¬ 
ment. And Marconi is still experimenting. 


Chapter 34 

SOME EXPERIMENTS IN PHYSICS 

Air Pressure.—Obtain a gallon can and fit the neck 
with a snug cork. Remove the cork and pour into the 
can enough water to cover the bottom well. Place the 
can over the Bunsen burner and bring the water to a 
boil. When the steam is issuing vigorously, insert the 
cork and quickly thrust the can under a cold water 
faucet or into a pail of cold water. The steam will 
condense on the inside, leaving a vacuum, and the pres¬ 
sure of the outside air will crush the can into an unrec¬ 
ognizable mass of tin. 

Floating Copper on Water.—Despite the fact that 
copper is nearly 9 times as heavy as water, you can 
float a copper wire. Allow a basin of cold water to 
stand for a short time. Cut several lengths of fine 
copper wire. Holding a piece two or three inches 
above the water drop it. The wire will curve the sur¬ 
face of the water downward and float in a shallow de¬ 
pression. Owing to what we call surface tension the 
surface of a body of still water behaves as though a 
tight membrane were stretched over it. 

Singing Flames.—Obtain two three-quarter inch 
gas pipes about 18 inches long. Clamp each in a ver¬ 
tical position to a ring-stand and place it over a Bunsen 

302 


3°3 


Some Experiments in Physics 

burner. Light one of the burners and lower the pipe 
over the flame. Then regulate the gas pressure until 
you get a musical note. In the same way start the 
other flame to singing. Make a paper cylinder about 
8 inches long and just large enough to slip over the 
pipes. With the two flames singing raise and lower 
the cylinder over one of the pipes until you will hear a 
distinct throbbing. This alternate increase and de¬ 
crease of the sound is shown as beats. By changing 
the length of the pipe you change the pitch of 
the sound produced, and, when two notes of differ¬ 
ent pitches are sounded together beats are heard. 
This is one of the chief causes of discord in 
music. 

If you have trouble in getting the Bunsen flame to 
sing, soften a piece of glass tubing in the flame and 
draw it out so as to make a jet tube. Substitute this 
for the burner, connecting it to the gas supply and 
lowering the pipe over the flame. 

Musical Pipes.—Secure a lamp chimney about 14 
inches long having straight sides and as small a diam¬ 
eter as possible. Clamp this in a vertical position to a 
ring-stand. Find a short length of thin walled brass 
tubing and flatten one end so that only a narrow slit is 
left. Connect the opposite end to an 18-inch length of 
rubber tubing. 

Blow across the mouth of the mounted chimney. 
A musical note will be obtained. You will need a little 
practice in order to know just how hard to blow and 
how to direct the air jet. Rest the chimney on the 


304 The Boys’ Own Book of Science 

table top and blow again. Now you have a closed 
pipe. You will notice that the tone is much lower in 
pitch. It is just an octave lower. 

Now fill a wide mouth bottle nearly full of water and 
lower the chimney into it. Adjust the chimney until 
the length of the air column (from the top of the chim- 



Producing a musical note by blowing across the mouth of a closed pipe. 

ney to the water) is 13.25 inches. Blow across the 
mouth and you will obtain the note known as middle C 
(fig- 35)- Lower the chimney until the air column is 
11.75 inches long and blow again. Now you obtain 
the next note of the scale. Continue to adjust the 
chimney, making in succession lengths of 10.5, 9.9, 8.8, 
7.9, 7, and 6.6 inches respectively. These various 


















Some Experiments in Physics 305 

lengths beginning with 13.25 and ending with 6.6 will 
give you the notes of the scale. 

If you can arrange a row of bottles, test tubes, or 
chimneys so as to secure all of these lengths at once, 
you may play the scale upon them. If you understand 
music you may play familiar airs. Such a stunt forms 
a most interesting and novel feature for an evening’s 
entertainment. 

An Air Thermometer.—Blow a bulb on the end of 
a glass tube just as you did in making the ether ther¬ 
mometer in the chapter on crystals. As before, select 
a piece of tubing having as thick walls as possible. If 
the first blow does not give a good bulb, remelt the 
glass and try again. Get as big a bulb as you can, but 
do not let the walls get too thin. Thrust the tube 
through a 2-hole stopper fitted into a small bottle or 
test tube containing colored water. Have the tube dip 
beneath the surface of the water (Fig. 36). Brush 
a Bunsen flame across the bulb once or twice. This 
will expand the air and force some of it out. When 
the bulb cools water will be drawn up the tube. Then 
as the temperature changes the water will rise and fall 
in the tube. As the air in the bulb cools and contracts, 
the water will rise. As it warms and expands, it will 
fall. Put a few drops of ether, carbon disulfide, or 
gasoline on the bulb and watch the water rise. The 
liquid cools the bulb by evaporation. Put a few drops 
on your hand and note the cooling effect. 

'‘Burning” Water.—Pour a little ether or gasoline 
on the surface of water in a beaker or evaporating dish. 


306 The Boys’ Own Book of Science 

Remove the ether or gasoline bottle to a safe distance. 
Then light the liquid. Apparently the water will take 
fire and burn. 

Boiling water without a flame is an interesting ex¬ 
periment. Fill a 500 c.c. flask half full of water and 

o 



Figure 36. 

Type of air thermometer invented by Galileo. 

bring it to a boil, driving out all the air. When the 
steam is coming well, turn off the gas, stopper the flask 
with a solid cork, and quickly invert it, supporting it 
by a tripod or ring-stand set in a large basin. Now 
pour cold water on the flask and the water will boil 
vigorously (Fig. 37). The water on the outside of 
the flask condenses the steam inside, making a vacuum 














Some Experiments in Physics 


and causing the water to boil at less than the usual 
temperature. If the flask is not a strong one, it will 
sometimes break. 



Boiling water at temperatures considerably below ioo° C. 

The production of heat by chemical action is seen 
in the mixing of sulfuric acid and water. Pour con¬ 
centrated sulfuric acid in a thin stream into a test tube 
half full of water. Note that the test tube becomes 
unbearably hot. 

Heat from the electric current may be well shown, 
if you have a lighting circuit in your laboratory. 
Stretch 12 feet of No. 28 iron wire from one 














308 The Boys’ Own Book of Science 

binding post to a wire suspended from the ceiling 
or other support and back to the other binding post. 
Darken the room and turn on the current. The wire 
will become red hot and sag just as telegraph wires do 
in the summer. Turn off the current and the wire will 
cool and shorten. 

Extremes of temperature in the same vessel may be 
shown with a test tube of water, a piece of ice, and a 
lump of lead or a coil of wire. Drop a piece of ice 
into a test tube and upon it the lead or push down the 
tube just above the ice a tightly fitting coil of wire. 
Fill the tube with water. Hold the upper portion of 
the tube in the flame. The water will boil there, but 
in the middle portion it will be cold, and in the bottom 
there will be ice. This proves that water is a poor 
conductor of heat. 

Conductivity of Metal, Glass, and Air.—Obtain 
two pint cans and a glass beaker of equal capacity. 
Set one of the cans into a small box containing a half 
inch layer of cotton wool or boiler felt. About the 
sides of the can stuff the box full of the packing mate¬ 
rial. Leave the other can in the open. Fill each can 
and the beaker with boiling water and cover each with 
a glass plate or square of asbestos. At intervals take 
the temperature of the water in each container. In 
which does it cool fastest? Slowest? The principle 
of the fireless cooker is illustrated in the can packed in 
cotton wool. Both the cotton and the wooden box are 
heat insulators, but the best insulator is the air in the 
spaces between the fibers of cotton. 


Some Experiments in Physics 309 

Convection Currents.—Heat is distributed through 
liquids and gases by currents set up by differences in 
density due to differences in temperature. Pour a 
quarter-inch depth of water into a tumbler and set in it 



a candle about an inch long. Light the candle and 
place over it a lamp chimney (Fig. 38). In a moment 
or two the flame will go out. It has burned out the 
oxygen and produced an atmosphere of carbon dioxide. 
Again light the candle and place over it the chimney, 
but divide the chimney by a cardboard partition ex- 
















310 The Boys’ Own Book of Science 

tending about two-thirds the way down its length. 
This time the flame will not go out. It will burn in¬ 
definitely and by its fluttering you will see that a current 
of air is passing through the apparatus. Hold a 
lighted match or a piece of touch paper on each side of 
the partition and you will see that air is passing down 
one side of the chimney and rising on the other. This 
experiment illustrates the principle of hot air heating. 
The air at the bottom of the chimney expands with the 
heat and becomes lighter than the cooler air above. 
Therefore the cold heavy air settles on one side of the 
partition and pushes up the warmer lighter air on the 
other side. 

Freezing Mixtures.—In a metal cup or can mix i 
part of salt with 3 parts of crushed ice or snow. Set 
the can on a block of wood having on the top of it a 
little water. Very shortly you will observe moisture 
collecting on the outside of the can and then a deep 
layer of frost. A thermometer thrust into the mixture 
will show temperatures considerably below zero. Pick 
up the can and you will find it frozen very securely to 
the block. Water in a test tube thrust into the ice 
will quickly freeze. 

By mixing 3 parts of calcium chloride with 2 parts of 
snow or ice, you may obtain a temperature low enough 
to freeze mercury. This means 40 degrees below 
zero. 

Making a Lifting Magnet.—An electromagnet that 
will prove to be a little giant and one which you may 
connect directly to a no-volt circuit may be easily 



Lifting 45 pounds with a homemade electromagnet. Its capacity is more than 200 
pounds. 


311 





















3 T 3 


Some Experiments in Physics 

made. Go to a blacksmith shop and get a rod of per¬ 
fectly soft iron about 18 inches long and I inch in 
diameter. Have the blacksmith bend this into the 
shape of the letter U. From heavy leather cut 4 
washers each about 5 inches in diameter and just large 
enough to fit snugly on the iron rod. Thrust two of 
them well up on the arms of the rod and place the 
others nearly at the bottom. Wind each arm between 
these washers with tape. Then buy several pounds of 
No. 26 double covered copper wire. Leaving long 
lead wires at the end, wind this wire as tightly and 
closely as possible between the washers on one arm. 
When this side has been filled carry the wire across and 
fill the space between the washers on the other arm. 
But in doing so be very sure that you wind the wire on 
the second arm in the same direction that you did on 
the first. That is, wind it so that if the rod were 
straightened out the wire would be wound in the same 
direction from end to end. To wind this wire will 
require considerable time, but the more you wind, the 
greater will be the lifting power of your magnet. 

When the wire is wound, make a soft iron hanger to 
fit across the poles. This should be a strip of quarter 
inch iron 1 inch wide and carrying a hook at the center. 

If you have used sufficient wire, the magnet may be 
safely connected to the no-volt lighting circuit. But, 
if in doing so, you notice that the winding seems to get 
hot break the circuit at once and, before using again, 
connect in series with it your lampboard rheostat, and 
turn on enough lamps to give you the maximum lifting 


314 The Boys’ Own Book of Science 

power without heating. Try its lifting power on bars 
of iron, nails, and spikes. If you have inserted a 
switch in the circuit, you may at any moment drop the 
load by opening the switch. The fact that an electromag¬ 
net may be made instantly to acquire or lose its magnet¬ 
ism is one of its chief advantages. Hang the magnet 
on a crowbar placed across two saw horses. Put the 
hanger across the poles and close the circuit. Attach 
to the hook the heaviest load you can find. You should 
be able to lift at least 100 pounds and probably more. 

A Pinhole Camera.—For this experiment you must 
have a room which you can make perfectly dark, and 
the shades at the windows should be black so that no 
light will come through them. Blankets may be hung 
over all but one of the windows, if necessary. Through 
the dark shade of this window make a hole about an 
eighth of an inch across and hold an 18-inch square of 
white bristol board 1 foot from it. If there is good 
sunlight outside, you will obtain an excellent image of 
the landscape and whatever happens to be within range. 
But you will notice that the image is inverted. This 
is always true of what we call real images. The rays 
of light reflected from the distant objects pass in 
straight lines through the small opening and come to 
focus on your screen. But in passing through the 
opening in the shutter, the rays cross and this inverts 
the image. 

“Burning” a Candle in a Beaker of Water.—Clamp 
in a vertical position on your “magic demonstration 
table” a pane of window glass. Raised on a block of 


Some Experiments in Physics 315 

wood about a foot in front of the glass set a candle. 
On a block of the same height and at the same distance 
behind the glass set a beaker, or bottle, of water. 
Light the candle and by reflection it will seem to be 
burning in the beaker of water. Light from the beaker 
is transmitted through the glass to your eye, and light 
from the candle is reflected from the glass to your eye. 
This image is upright as you see, and is called a virtual 
image. It is the same size as the object and as far 
behind the mirror as the object is in front. Move to 
either side of the room and find how far you can go 
and still see the image of the candle. The wider the 
pane of glass, the greater this distance will be. 

Near-sightedness and Far-sightedness.—For this 
experiment you will need a double concave lens of about 
15 centimeters focal length and two double convex 
lenses of about 20 to 25 centimeters focal length. 
Make a wire holder for one of the convex lenses and 
mount it on a yardstick. Standing a little ways back 
from an open window, hold the lens so as to catch the 
light coming through the window and place behind it a 
white cardboard screen. Move the screen until you 
obtain a distinct image of the landscape. The distance 
between the lens and the screen will be the focal length 
of the lens. The crystalline lens of the eye produces 
an inverted real image upon the retina in exactly the 
same way. 

Now in a darkened room place the yardstick length¬ 
wise of the table and secure it in position with blocking 
at one end. Place a lighted candle on one side of the 


316 The Boys } Own Book of Science 

lens at a distance of about twice the focal length. On 
the other side place the screen and move it back and 



A 





C 

Figure 39. 

A shows a normal eye with the image of a distant object brought to focus 
on the retina; B shows the condition for a near-sighted eye; and C shows it 
for a far-sighted eye. 

forth until you obtain a clear image. The lens corre¬ 
sponds to the crystalline lens of the eye and the screen 
to the retina. Unless the image on our retinas is clear 















Some Experiments in Physics 317 

and distinct, our sense of vision will be blurred. Move 
the screen toward the lens. The image is now indis¬ 
tinct. Move it a little back of its original position and 
the image will again be indistinct. 

The lens of the eye is the most remarkable lens in 
the world. In a normal eye it is able to change its 
focal length according to the distance of the object so 
as always to bring the image to focus on the retina. 
But in a near-sighted eye, unless an object is held 
closer to the eye than is necessary for a normal indi¬ 
vidual, the image will come to focus in front of the 
retina. The result is a blurred impression. In a far¬ 
sighted eye, the image comes to focus behind the retina, 
unless the object is held farther away from the eye than 
is necessary for normal sight. You illustrated near¬ 
sightedness when you held the screen farther away 
from the lens than the position for a distant image, 
and far-sightedness when you held it nearer to the 
lens. 

To show how near-sightedness is corrected, hold 
the screen a little behind the position necessary for a 
clear image. Then hold between the candle and the 
lens the double concave lens. Move it back and forth 
until you obtain a clear image on the screen. That is 
what glasses do for near-sighted people. Concave 
lenses diverge the rays of light just enough to bring 
the image to focus on the retina instead of in front 
of it. 

To show how far-sightedness is corrected, hold the 
screen a little in front of the position necessary to se- 


318 The Boys’ Own Book of Science 

cure a distinct image. The image will be blurred. 
Then hold between the candle and the lens the other 
convex lens. Move it back and forth until you obtain 
a clear image on the screen. The convex lens con¬ 
verges the rays of light and brings them to focus on the 
retina. 

A Compound Microscope.—A compound micro¬ 
scope consists of an objective and an eyepiece. Both 
are convex lenses. The objective is of shorter focal 
length than the eyepiece. To make a microscope select 
two double convex lenses, one of about 5 cm. focal 
length and the other of about 10 cm. You can always 
determine the focal length by focusing the image of a 
distant object on a screen and measuring the distance 
between the image and the lens. Mount the objective 
in the jaws of a clamp attached to a ring-stand and 
place it just a little more than its focal length from the 
table top. In another clamp directly above the first 
mount the eyepiece so that the centers of the lenses are 
in the same straight line. Now place a sample of fine 
type on the table beneath the objective and move the 
eyepiece up and down until you get a distinct image. 
The farther you can separate the lenses and still 
get a clear image, the greater will be the magnifying 
power of your microscope. You will observe that the 
image is inverted. If you wish to move the image in 
one direction, you must move the object in the opposite 
direction. 

Scientists have already reached the limit of magnifi¬ 
cation with compound microscopes. The limit for 


Some Experiments in Physics 319 

practical work is about 1200 diameters, although mag¬ 
nifications of 3000 diameters have been obtained. 

A Galilean Telescope.—Galileo, a famous Italian 
scientist, first explored the heavens with a telescope in 
1608. With his simple instrument he made marvelous 
discoveries. He revealed the moons of Jupiter, he 
disclosed new stars, and resolved the beautiful Milky 
Way into a countless host of infinitely distant suns. 

The common opera glass is made on the same prin¬ 
ciple as Galileo’s telescope. It will be easy for you to 
arrange lenses to illustrate this telescope yourself. 
Mount in a wire holder on a yardstick a double convex 
lens of about 10 to 15 inches focal length for the ob¬ 
jective and a double concave lens of 4 to 6 inches focal 
length for the eyepiece. Adjust the lenses so their 
centers are in a straight line and point them toward 
some not too distant object. Move the eyepiece back 
and forth until you get a distinct image. You will ob¬ 
serve that the image is upright and that you secure 
considerable magnification, or better distant objects 
seem to be brought nearer. 

An Astronomical Telescope.—It is entirely possible 
for any boy to make an astronomical telescope of con¬ 
siderable power and one which will afford him a great 
deal of pleasure. The first consideration in making a 
telescope is to secure the lenses. You will need two— 
a double convex lens of long focal length for the ob¬ 
jective and one of short focal length for the eyepiece. 
The greater the difference in these focal lengths, the 
greater will be the magnifying power. If the objec- 



320 The Boys’ Own Book of Science 

tive has a focal length of 36 inches and the eyepiece is 
2 inches in focal length, the telescope will magnify 
18 times. And those numbers will be about the 
proper lengths. The eyepiece may be from 2 to 4 
inches. 

The next essential is a heavy cardboard cylinder just 
large enough in diameter to take the objective and as 
long as its focal length. At a stationer’s or some 
supply house dealing in wrapping paper and mailing 
devices possibly you can find such a cylinder. If 
not, you will have to make a cylinder. To do so cut a 
length from a curtain pole or some other round stick of 
wood having the same diameter as the lens. Then 
obtain a number of sheets of heavy wrapping paper 
and prepare a pot of glue or paste such as a paper- 
hanger uses. Cut the paper to the exact length of the 
pole. Lay a strip of it on the table and roll it once 
about the pole. With a brush spread paste on the un¬ 
rolled portion of the strip and roll it very tightly about 
the pole. Repeat this with other strips until you have 
a cylinder of the proper thickness. After it has dried 
well, remove the pole and your telescope tube is ready. 

You must now mount the objective. Just inside one 
end of the tube paste a narrow ring of cardboard, being 
sure that the distance between it and the end of the 
tube is everywhere the same. Slip the objective into 
place letting it rest against this cardboard ring. Secure 
it there with another cardboard ring. 

Now you are ready for the eyepiece. Since this lens 
is of smaller diameter, it must be mounted in a smaller 


3 21 


Sortie Experiments in Physics 

tube. Prepare another paper cylinder just large 
enough to hold the lens and about 3 or 4 inches longer 
than its focal length. Place the eyepiece in one end 
just as you did the objective, but to enable you to see 
to the best advantage only the center portion of the 
glass should be exposed. Therefore, directly in front 
of the eyepiece place a cardboard disk having a small 
hole about an eighth to a quarter of an inch in diameter 
exactly in its center. Just inside the big tube place a 
disk of wood about an inch thick and having a hole 
bored in it just large enough to take the smaller tube 
and to permit of its being freely moved back and forth. 


1 

7 


E 

1 

■ r~ 

L= 


Figure 40. 

Astronomical Telescope. 


Insert the eyepiece tube and your telescope will be 
ready for its first try-out. (Fig. 40.) 

For distinct vision the eyepiece should be drawn out 
until the distance between it and the objective is equal 
to the sum of the focal lengths of the lenses. Point 
the instrument toward a distant object and bring it 
into focus. Of course it will be magnified and appear 
much nearer, but you will be surprised possibly at one 
thing. The image will be inverted. In an astro¬ 
nomical telescope this makes no difference. It does 
not matter if the moon is upside down. In field 
glasses, however, another lens system must be used to 














322 The Boys Own Book of Science 

reinvert the image. This results in some loss of light 
and is unnecessary in an astronomical telescope. 

You will find it difficult to hold your instrument 
steady enough to keep an object in the field of vision. 
You will need a support. Three small curtain poles or 
old broom sticks and a little ingenuity will enable you 
to contrive one. 

On a clear night explore the moon. It is the most 
beautiful object of the heavens. Examine its craters 
and rugged mountains. I am sure you will be de¬ 
lighted with the results. Of course you cannot mag¬ 
nify the stars. Their distances from us are too im¬ 
mense. But the planets Venus and Jupiter will be well 
worth your attention. 


Chapter 35 

“THE HALL OF FAME” 


D uring my college days the members of my fra¬ 
ternity carried out a novel stunt in the way of 
evening entertainment. In the attic of the “frat” 
house we made a plaster of Paris cast of each mem¬ 
ber’s face. Then on the walls of a small room draped 
with black cloth and dimly lighted with candles, so as 
to produce as weird an effect as possible, we hung the 
casts. Each one was numbered, and each guest was 
required to pass judgment upon the identity of each 
cast. In a little booklet he recorded his guesses, for 
in many instances they were little more than that. It 
is no easy matter correctly to connect a particular cast 
with the owner’s face. If you did not know your own, 
you quite likely would be at a loss to pick it out. 

This performance is really of a chemical nature, for 
we must know that plaster of Paris is gypsum with half 
of its water of crystallization driven off, and that when 
it sets it unites chemically with this water again. 

To make these casts, select some old shop or room 
in which the muss which it will make will not matter. 
Have at hand a large quantity of plaster of Paris, a 
supply of water, and plenty of vaseline. Each aspi¬ 
rant to the honor of being included in this “hall of 

323 


324 The Boys’ Own Book of Science 

fame” must first grease his face thoroughly with vase¬ 
line. Be sure that the eye-lashes, eyebrows, and every 
part that will be touched by the mixture are well 
covered. If not, the experience in removing the first 
impression will be very painful. I have seen boys al¬ 
most weep at this part of the operation. 

An old bench or cot may serve as operating table. 
Lay the victim upon it, wrap a towel about his face to 
hold the plastic mass in place, and do not forget to 
insert in his nostrils two paper tubes, through which he 
may breathe while cut off from the outer world. Apply 
a rather thick mixture of plaster of Paris and water 
liberally, making a layer at least an inch thick. For 
the patient there will be perfect darkness, and he will 
be unable to speak. Presently he will have evidence 
that a chemical change is taking place in the mixture on 
his face. He will feel the gentle warmth from the 
heat developed in the chemical union of the water and 
plaster of Paris. After about 15 minutes, the mixture 
will have set, and the cast may be removed. To do 
this stand up, hold your hands over the cast, and shake 
and pull it off. If the face has been well vaselined, this 
will be a very simple matter. 

You now have the form in which the finished cast 
will be molded. Vaseline the inside of this mold thor¬ 
oughly and fill it with another mixture of the plaster of 
Paris. While the mixture is still soft insert a wire 
loop with which to hang the cast in the “hall of fame.” 
When this second mixture has hardened, break away 
the first cast by pounding it gently with a wooden 


“The Hall of Fame n 


325 


mallet. Retouch the cast by filling all the pores and 
cavities with some fresh mixture and paint it with 
white enamel. You will be delighted with the result. 

Hang these in the chosen room. If it is properly 
draped and lighted, the effect may be made weird and 
ghostlike. I have never seen a more unusual or more 
interest provoking event at an evening’s entertainment 
than this. Try it. 


SOURCES OF SUPPLY 


Some of the apparatus and material needed to 
perform the experiments described in the foregoing 
pages may be found in the home or had from the 

grocer and the local druggist. Real apparatus and 

many of the chemicals must be purchased from some 
supply house. Following is a list of firms located in 
various parts of the country: 

Cambridge Botanical Supply Co., Waverly, Mass. 

Central Scientific Co., Chicago, Ill. 

W. M. Welch Scientific Co., Chicago, Ill. 

Denver Fire Clay Co., Denver, Colo. 

Eimer and Amend, New York, N. Y. 

Braun-Knecht-Heimann Co., San Francisco, Calif. 

Possibly some of these companies will send you 

catalogues, if you request it and explain that you 

are starting a home laboratory. Select the experi¬ 
ments which you wish to do first. Then purchase your 
equipment. Let it be good and take care of it. 


326 


INDEX 


A 

Acetates, 280 
Acetylene lamp, 186 
Acid, hydrochloric, 81 
Acid, nitric, 83 
Acid, phenol-sulfonic, ick, 
Acid, sulfanilic, 105 
Acids, 73, 223 
Air, 27, 57 
Air, burning, 182 
Air pressure, 302 
Alchemist, 17 
Alcohol, grain, 252 
Alcohol, wood, 252 
Alloys, 164 
Alum crystals, 293 
Alum, test for, 264 
Aluminum, 171, 207 
Alundum, 149 
Ammonia, 33, 104 
Ammonium salts, 265 
Analysis, 273 
Analysis of water, 109 
Anode, 220 
Arc furnace, 149 
Asbestos, 149 
Atmosphere, 57 


B 

Baking powder, 262 
Base, preparation of, 86 
Bases, 73, 223 
Berzelius, Jons Jacob, 146 
Bessemer, Sir Henry, 214 
Bleaching, 136, 139 
Blowpipe tests, 283 


Blue-printing, 238 
Blue vitriol, 23, 219, 224 
Boiling, 298, 306 
Boneblack filter, 93 
Borates, 280 
Borax, 126, 267 
Borax bead tests, 282 
Boric acid, 267 
Brass, 157 
Bromides, 273 
Bromine, 207 
Bronze Age, 164 
Bunsen burner, 8, 181 
Burettes, 77 
Burning, 41 

Burning tests for fibers, 127 
Butter, 266 

C 

Calcium, test for, 265 
Camera, pinhole, 314 
Cane sugar, 261 
Carbohydrates, 259 
Carbonates, 125, 279 
Carbon dioxide, 63, 64, 192 
Cathode, 220 

Cavendish, Sir Henry, 49, 57 
Cell, bichromate, 217 
Cell, gravity, 218 
Cell, simple, 232 
Cells, electric, 217 
Charcoal, 42, 160, 204 
Chemical magic, 17 
Chlorates, 279 
Chlorides, 102, 273 
Chlorine in water, 101 
Chlorine, preparation of, 274 
Chromates, 280 




Index 


Chrome yellow, 145 
Coal tar dyes, 268 
Cobalt nitrate tests, 283 
Coke oven, 159 
Color experiments, 21, 74 
Combustion, 42, 45, 179 
Condenser, Liebig, 98 
Convection currents, 309 
Copper, floating, 302 
Copper, metallurgy of, t6o 
Copper oxide, 162 
Copper salts, 269 
Corks, 12 
Cotton, 127, 130 
Crystal garden, 297 
Crystals, 289 


D 


Daguerre, 241 

Davy, Sir Humphry, 116, 149, 233 
Definite proportions, Law of, 292 
Distillate, 98 
Distillation, 96 
Dust explosion, 48 


Fat, test for, 261 
Filter, boneback, 93 
Filter paper, 13 
Filter, sand, 94 
Filtrate, 93 
Filtration, 90 
Fire clay, 149 
Fire extinguishers, 190 
Fire, green, 203 
Fire, purple, 203 
Fire, red, 203 
Fire, white, 202 
Firew'orks, 202 
Flames, singing, 302 
Flame tests, 281 
Flash powder, 202 
Food tests, 258 
Formaldehyde, 254 
Freezing mixtures, 310 
“Freezing” water, 18 
Furnace, arc, 149 
Furnace, combustion, 160 
Furnace, crucible, 157 
Furnace, resistance, 153 
Furnaces, electric, 148 


E 

Edison, Thomas A., 247 
Efflorescent salts, 291 
Electric cells, 217 
Electric current, 216 
Electric furnaces, 148 
Electrolysis apparatus, 219 
Electrolytes, 222 
Electromagnet, 310 
Electroplating, 224 
Electrotyping, 228 
End-point, 76 
Ether thermometer, 298 
Evaporation, 62 
Explosion, gas, 208 


F 

Faraday, Michael, 134 
Farsightedness, 315 


G 

s 

Galvanizing iron, 171 
Gas explosion, 208 
Gas, illuminating, 47 
Gas, producer, 197 
Gas, water, 161 
Gasoline, 21, 47 
German silver wire, 152 
Glass bending, 11 
Glass cutting, 8 
Glauber’s salt, 298 
Glucose, 260 
“Gold,” 293 
Gunpowder, 204 
Gypsum, 22 

H 

Hall of Fame, 323 

Hard water, 109 

Heat by chemical action, 307 



Index 


329 


Heat conductivity, 308 
Heating apparatus, 12 
Heating metals, 166 
Henry, Joseph, 200 
Home laboratory, 1 
Hydrochloric acid, 81 
Hydrogen, 38, 50, 162 
Hydrogen, preparation of, 49 
Hypo, 18, 243 

I 

Indicators, 73 
Ink, sympathetic, 30 
Iodide, nitrogen, 212 
Iodides, 277 
Iodine, 207, 212 
Iodine crystals, 294 
Ions, 232 

Iron tests, 239, 284 



Kerosene, flashing point of, 198 


L 

Laboratory hints, 12 
Lavoisier, 71 
Lead, 106, 168, 284, 293 
Lemon extract, 269 
Liebig condenser, 98 
Liebig, Justus von, 177 
Lifting magnet, 310 
Light, chemistry of, 237 
Linen, 127 
Litmus, 73 
Local action, 232 
Lye, 119 

M 

Magic, chemical, 17 
Magic fountain, 33 
Magic wand, 24 
Magic writing papers, 30 
Magnesium, 42 


Marconi, 300 
Match, safety, 199 
Mercury, 284 
Metals, 33, 164, 173, 280 
Methyl orange, 73 
Microscope, compound, 318 
Milk, 266 

Minerals in water, 114 
Moisture in the air, 68 
Mordant, 145 


N 

Naphthyl amine hydrochloride, 
National colors, 17, 203 
Nearsightedness, 315 
Negative, 244 
Nessler’s reagent, 104 
Neutralization, 76 
Nichrome wire, 152 
Nitrates, 104, 278 
Nitric acid, 83 
Nitrites, 104 
Nitrogen, 69 

Nitrogen compounds, 104 
Nitrogen iodide, 212 
Non-electrolytes, 222 
Non-metal, 165 

O 

Oleomargarine, 267 
Olive oil, 269 

Organic matter, 101, 106, 288 
Oxalates, 279 
Oxidation, 48 
Oxygen, 38, 60 

Oxygen, preparation of, 39, 41 


P 

Perkin, Sir William, 235 
Permanent hardness, 112 
Permanganates, 280 
Phenolphthalein, 21, 73 
Phenol-sulfonic acid 103 
Phosphates, 106, 279 


105 



330 


hid ex 


Phosphorus, 42, 46, 189 
Photography, 241 
Pinhole camera, 314 
Pipes, musical, 303 
Plaster of Paris, 323 
Polarization, 232 
Potassium chlorate, 39, 203 
Potassium nitrate, 204, 270, 291 
Potassium permanganate, 24, 106 
Precipitate, 94 
Preservatives, milk, 267 
Priestley, 35 
Proteid, test for, 262 


a 

Quicklime, 159 

R 

Reducing agent, 52 
Reduction, 52 

Replacement of metals, 173 
Resistance furnace, 153 
Rheostat, German silver wire, 
152 

Rheostat, lampboard, 150 
Rheostat, Nichrome wire, 152 


S 

Saccharin, 268 
Safety lamp, 185 
Safety match, 199 
Salt, preparation of, 75 
Salts, 73 

Saponification, 119 
Scheele, 35 

Separation of lead, silver, and 
mercury, 287 
Silk, 127, 129, 130 
Silver, 174, 284 
Silver nitrate, 102 
Silver plating, 229 
Silver salts in photography, 229 
Simple cell, 232 
Smoke rings, 188 


Soap, 119 

Soap bubbles with hydrogen, 55 
Soap, cleansing action of, 124 
Soap powder, 125 
Soap, soft, 123 

Soap test for hard water, 109 
Sodium chloride, chemically pure, 
294 

Soft water, 109 

Solder, 167 

Sparkler, 207 

Special tests, 252 

Spontaneous combustion, 45 

Stains, 136 

Starch test, 259 

Steel wool, 41 

Still, 97 

Stoppers, 11 

Storage cell, 230 

Sulfanilic acid, 105 

Sulfates, test for, 264, 278 

Sulfides, 278 

Sulfites, 278 

Sulfites in canned goods, 270 
Sulfur, 29, 45, 204 
Sulfur crystals, 292 
Supersaturation, 294 
Supply houses, 326 

T 

Tartrates, test for, 263, 279 
Telescope, astronomical, 319 
Telescope, Galilean, 319 
Temporary hard water, no 
Tests, qualitative, 252 
Textile fibers, 127 
Thermit, 171 
Thermometer, air, 305 
Thermometer, ether, 298 
Titration, 77 
Total solids, 100 
Touch paper, 202 


V 

Vanilla extract, 269 



/ tide;X 


w 


Water, 22, 89 
Water, distilled, 96 
Water gas, 161 
Water glass, 149, 297 
Water, hard, 109 
Water, minerals in, 109 
Water, purification of, 90, 98, 99 
Water, sanitary examination of, 
99 


Water, soft, 109 
Westinghouse, George, 27 
White fire, 202 
“Wine,” 23 
Wood’s metal, 168 
Wool, 127, 130 


Z 

Zinc dust, 45, 208 





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